ARM: Add optimised swahb32() byteswap helper for v6 and above

ARMv6 and later processors have the REV16 instruction, which swaps
the bytes within each halfword of a register value.

This is already used to implement swab16(), but since the native
operation performaed by REV16 is actually swahb32(), this patch
renames the existing swab16() helper accordingly and defines
__arch_swab16() in terms of it.  This allows calls to both swab16()
and swahb32() to be optimised.

The compiler's generated code might improve someday, but as of
4.5.2 the code generated for pure C implementing these 16-bit
bytesswaps remains pessimal.

swahb32() is useful for converting 32-bit Thumb instructions
between integer and memory representation on BE8 platforms (among
other uses).

Signed-off-by: Dave Martin <dave.martin@xxxxxxxxxx>
scripts: setlocalversion: do not append plus sign
Added optimized CRC32 algorithm.
Remove ARM sha1 routines

Since commit 8827a4a6b397b07a341ba7fd36ffb91a7835207d
("lib/sha1: use the git implementation of SHA-1"), the ARM SHA1
routines no longer work. The reason? They depended on the larger
320-byte workspace, and now the sha1 workspace is just 16 words
(64 bytes). So the assembly version would overwrite the stack randomly.

The optimized asm version is also probably slower than the new improved
C version, so there's no reason to keep it around.  At least that was
the case in git, where what appears to be the same assembly language
version was removed two years ago because the optimized C BLK_SHA1 code
was faster.

Reported-and-tested-by: Joachim Eastwood <manabian@gmail.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Added optimized ARM RWSEM algorithm.