crypto: lib/sha1 - rename "sha" to "sha1"

The library implementation of the SHA-1 compression function is
confusingly called just "sha_transform()".  Alongside it are some "SHA_"
constants and "sha_init()".  Presumably these are left over from a time
when SHA just meant SHA-1.  But now there are also SHA-2 and SHA-3, and
moreover SHA-1 is now considered insecure and thus shouldn't be used.

Therefore, rename these functions and constants to make it very clear
that they are for SHA-1.  Also add a comment to make it clear that these
shouldn't be used.

For the extra-misleadingly named "SHA_MESSAGE_BYTES", rename it to
SHA1_BLOCK_SIZE and define it to just '64' rather than '(512/8)' so that
it matches the same definition in <crypto/sha.h>.  This prepares for
merging <linux/cryptohash.h> into <crypto/sha.h>.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>