lib/crypto: powerpc/sha1: Migrate optimized code into library

lib/crypto: powerpc/sha1: Migrate optimized code into library

Instead of exposing the powerpc-optimized SHA-1 code via
powerpc-specific crypto_shash algorithms, instead just implement the
sha1_blocks() library function.  This is much simpler, it makes the
SHA-1 library functions be powerpc-optimized, and it fixes the
longstanding issue where the powerpc-optimized SHA-1 code was disabled
by default.  SHA-1 still remains available through crypto_shash, but
individual architectures no longer need to handle it.

Note: to see the diff from arch/powerpc/crypto/sha1-spe-glue.c to
lib/crypto/powerpc/sha1.h, view this commit with 'git show -M10'.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250712232329.818226-11-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>