s390/qdio: remove unneeded sanity check in qdio_do_sqbs()

All callers of set_buf_states() are already making sure that 'count'
is not 0. So don't check it an additional time.

Note that our own code also doesn't _require_ the count to be sane
(ie. we can't overrun an array or similar). So worst case HW would
simply reject the SQBS operation and report an error.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>