powerpc: Add a powerpc implementation of SHA-1

This patch adds a crypto driver which provides a powerpc accelerated
implementation of SHA-1, accelerated in that it is written in asm.

Original patch by Paul, minor fixups for upstream by moi.

Lightly tested on 64-bit with the test program here:

 http://michael.ellerman.id.au/files/junkcode/sha1test.c

Seems to work, and is "not slower" than the generic version.

Needs testing on 32-bit.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>