nios2: add FORCE for vmlinuz.gz

Add FORCE to placate a warning from make:

arch/nios2/boot/Makefile:24: FORCE prerequisite is missing

Fixes: 2fc8483fdcde ("nios2: Build infrastructure")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>

nios2: move the install rule to arch/nios2/Makefile

Currently, the install target in arch/nios2/Makefile descends into
arch/nios2/boot/Makefile to invoke the shell script, but it is no
good reason to do so.

arch/nios2/Makefile can run the shell script directly.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

kbuild: consolidate Devicetree dtb build rules

There is nothing arch specific about building dtb files other than their
location under /arch/*/boot/dts/. Keeping each arch aligned is a pain.
The dependencies and supported targets are all slightly different.
Also, a cross-compiler for each arch is needed, but really the host
compiler preprocessor is perfectly fine for building dtbs. Move the
build rules to a common location and remove the arch specific ones. This
is done in a single step to avoid warnings about overriding rules.

The build dependencies had been a mixture of 'scripts' and/or 'prepare'.
These pull in several dependencies some of which need a target compiler
(specifically devicetable-offsets.h) and aren't needed to build dtbs.
All that is really needed is dtc, so adjust the dependencies to only be
dtc.

This change enables support 'dtbs_install' on some arches which were
missing the target.

Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Paul Burton <paul.burton@mips.com>
Acked-by: Ley Foon Tan <ley.foon.tan@intel.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-kbuild@vger.kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-mips@linux-mips.org
Cc: nios2-dev@lists.rocketboards.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-xtensa@linux-xtensa.org
Signed-off-by: Rob Herring <robh@kernel.org>

nios2: use common rules to build built-in dtb

Using the common build support for built-in dtb files just requires
adding a .dtb.o target to obj-y.

This has the side effect that CONFIG_NIOS2_DTB_SOURCE should now be just
the dts filename in arch/nios2/boot/dts/ directory. Before any path was
supported, but if you want to build in your dtb to the kernel, it should
be in the kernel tree.

Cc: Ley Foon Tan <lftan@altera.com>
Cc: nios2-dev@lists.rocketboards.org
Signed-off-by: Rob Herring <robh@kernel.org>

nios2: build .dtb files in dts directory

Align nios2 with other architectures which build the dtb files in the
same directory as the dts files. This is also in line with most other
build targets which are located in the same directory as the source.
This move will help enable the 'dtbs' target which builds all the dtbs
regardless of kernel config.

This transition could break some scripts if they expect dtb files in
the old location.

Cc: Ley Foon Tan <lftan@altera.com>
Cc: nios2-dev@lists.rocketboards.org
Signed-off-by: Rob Herring <robh@kernel.org>

kbuild: clean up *.dtb and *.dtb.S patterns from top-level Makefile

We need to add "clean-files" in Makfiles to clean up DT blobs, but we
often miss to do so.

Since there are no source files that end with .dtb or .dtb.S, so we
can clean-up those files from the top-level Makefile.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rob Herring <robh@kernel.org>

nios2: Add support for compressed kernel

Signed-off-by: Ley Foon Tan <lftan@altera.com>

nios2: Build infrastructure

This patch adds Makefile and Kconfig files required for building a
nios2 kernel.

Signed-off-by: Ley Foon Tan <lftan@altera.com>