crypto: n2 - Rename arrays to avoid conflict with crypto/sha256.h

Rename the sha*_init arrays to n2_sha*_init so that they do not conflict
with the functions declared in crypto/sha256.h.

Also rename md5_init to n2_md5_init for consistency.

This is a preparation patch for folding crypto/sha256.h into crypto/sha.h.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>