s390/diag: Return errno's from diag204

Return different errno's from diag204 to allow users to handle them
accordingly. Instead of returning -1 regardless of the failing
condition, return -EINVAL on invalid memory address and -EOPNOTSUPP when
diag instruction fails.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Tobias Huschle <huschle@linux.ibm.com>
Signed-off-by: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>