crypto: sparc - rename sha256 to sha256_alg

To avoid a naming collision when we add a sha256() library function,
rename the "sha256" static variable in sha256_glue.c to "sha256_alg".
For consistency, also rename "sha224" to "sha224_alg".

Reported-by: kernel test robot <lkp@intel.com>
Cc: sparclinux@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>