lib/sha1: use the git implementation of SHA-1

For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem. The speed of the kernel sha-1 implementation has a major
impact on our boot performance.

To improve boot performance, we investigated using the heavily
optimized sha-1 implementation used in git. With the git
sha-1 implementation, we see a 11.7% improvement in boot time.

10 reboots, remove slowest/fastest.

Before:

Mean: 6.58 seconds Stdev: 0.14

After (with git sha-1, this patch):

Mean: 5.89 seconds Stdev: 0.07

The other cool thing about the git SHA-1 implementation is that
it only needs 64 bytes of stack for the workspace while the original
kernel implementation needed 320 bytes.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
CC: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
CC: Nicolas Pitre <nico@cam.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: David S. Miller <davem@davemloft.net>
CC: linux-crypto@vger.kernel.org
arm: remove "optimized" SHA1 routines

Since commit 1eb19a12bd22 ("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>
arm: remove export for removed "optimized" SHA1 routines

This fixes the sha_transform exported twice compilation warning.