s390/crypto: prng: Use -ENODEV instead of -EOPNOTSUPP

Let's use the error value that is typically used if HW support is not
available when trying to load a module - this is also what systemd's
systemd-modules-load.service expects.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>