[S390] qdio: leave inbound SBALs primed

It is not required to change the state of primed SBALs. Leaving them
primed saves a SQBS instruction under z/VM.

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