[S390] cio: Export chsc_error_from_response().

Make chsc_error_from_response() available to chsc callers outside
of chsc.c (namely qdio) to avoid duplicating error checking code.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>