powerpc/crc32: expose CRC32 functions through lib

Move the powerpc CRC32C assembly code into the lib directory and wire it
up to the library interface.  This allows it to be used without going
through the crypto API.  It remains usable via the crypto API too via
the shash algorithms that use the library interface.  Thus all the
arch-specific "shash" code becomes unnecessary and is removed.

Note: to see the diff from arch/powerpc/crypto/crc32c-vpmsum_glue.c to
arch/powerpc/lib/crc32-glue.c, view this commit with 'git show -M10'.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20241202010844.144356-9-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

arch/powerpc/crypto/Kconfig

@@ -13,19 +13,6 @@ config CRYPTO_CURVE25519_PPC64
 	  Architecture: PowerPC64
 	  - Little-endian
 
-config CRYPTO_CRC32C_VPMSUM
-	tristate "CRC32c"
-	depends on PPC64 && ALTIVEC
-	select CRYPTO_HASH
-	select CRC32
-	help
-	  CRC32c CRC algorithm with the iSCSI polynomial (RFC 3385 and RFC 3720)
-
-	  Architecture: powerpc64 using
-	  - AltiVec extensions
-
-	  Enable on POWER8 and newer processors for improved performance.
-
 config CRYPTO_CRCT10DIF_VPMSUM
 	tristate "CRC32T10DIF"
 	depends on PPC64 && ALTIVEC && CRC_T10DIF
@@ -40,7 +27,7 @@ config CRYPTO_CRCT10DIF_VPMSUM
 
 config CRYPTO_VPMSUM_TESTER
 	tristate "CRC32c and CRC32T10DIF hardware acceleration tester"
-	depends on CRYPTO_CRCT10DIF_VPMSUM && CRYPTO_CRC32C_VPMSUM
+	depends on CRYPTO_CRCT10DIF_VPMSUM && CRYPTO_CRC32C && CRC32_ARCH
 	help
 	  Stress test for CRC32c and CRCT10DIF algorithms implemented with
 	  powerpc64 AltiVec extensions (POWER8 vpmsum instructions).