crypto: s390/sha256 - rename module to sha256-s390

When the s390 SHA-256 code is built as a loadable module, name it
sha256-s390.ko instead of sha256.ko.  This avoids a module name
collision with crypto/sha256.ko and makes it consistent with the other
architectures.

We should consider making a single module provide all the SHA-256
library code, which would prevent issues like this.  But for now this is
the fix that's needed.

Fixes: b9eac03e ("crypto: s390/sha256 - implement library instead of shash")
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Closes: https://lore.kernel.org/r/20250529110526.6d2959a9.alex.williamson@redhat.com/


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