[S390] qdio: extract all primed SBALs at once

For devices without QIOASSIST primed SBALS were extracted in a loop.
Remove the loop since get_buf_states can already return more than
one primed SBAL.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>