csky: Remove unused $(dtb-y) from boot/Makefile

arch/csky/boot/Makefile does not build DTB,
arch/csky/boot/dts/Makefile does.

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

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

csky: Build infrastructure

This patch adds Makefile, Kconfig for build infrastructure.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>