MIPS: Drop 32-bit asm string functions

We have assembly implementations of strcpy(), strncpy(), strcmp() &
strncmp() which:

- Are simple byte-at-a-time loops with no particular optimizations. As
a comment in the code describes, they're "rather naive".

- Offer no clear performance advantage over the generic C
implementations - in microbenchmarks performed by Alexander Lobakin
the asm functions sometimes win & sometimes lose, but generally not
by large margins in either direction.

- Don't support 64-bit kernels, where we already make use of the
generic C implementations.

- Tend to bloat kernel code size due to inlining.

- Don't support CONFIG_FORTIFY_SOURCE.

- Won't support nanoMIPS without rework.

For all of these reasons, delete the asm implementations & make use of
the generic C implementations for 32-bit kernels just like we already do
for 64-bit kernels.

Signed-off-by: Paul Burton <paul.burton@mips.com>
URL: https://lore.kernel.org/linux-mips/a2a35f1cf58d6db19eb4af9b4ae21e35@dlink.ru/
Cc: Alexander Lobakin <alobakin@dlink.ru>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: linux-mips@vger.kernel.org

mips: Kconfig: Add ARCH_HAS_FORTIFY_SOURCE

FORTIFY_SOURCE detects various overflows at compile and run time.
(6974f0c4555e ("include/linux/string.h:
add the option of fortified string.h functions)

ARCH_HAS_FORTIFY_SOURCE means that the architecture can be built and
run with CONFIG_FORTIFY_SOURCE.

Since mips can be built and run with that flag,
select ARCH_HAS_FORTIFY_SOURCE as default.

Signed-off-by: Dmitry Korotin <dkorotin@wavecomp.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org

MIPS: Whitespace cleanup.

Having received another series of whitespace patches I decided to do this
once and for all rather than dealing with this kind of patches trickling
in forever.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: Move headfiles to new location below arch/mips/include

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>