crypto: sha256_generic - Switch to the generic lib/crypto/sha256.c lib code

Drop the duplicate generic sha256 (and sha224) implementation from
crypto/sha256_generic.c and use the implementation from
lib/crypto/sha256.c instead.

"diff -u lib/crypto/sha256.c sha256_generic.c" shows that the core
sha256_transform function from both implementations is identical and
the other code is functionally identical too.
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -855,6 +855,7 @@ config CRYPTO_LIB_SHA256
 config CRYPTO_SHA256
 	tristate "SHA224 and SHA256 digest algorithm"
 	select CRYPTO_HASH
+	select CRYPTO_LIB_SHA256
 	help
 	  SHA256 secure hash standard (DFIPS 180-2).