scsi: cxlflash: Separate RRQ processing from the RRQ interrupt handler

In order to support processing the HRRQ by other means (e.g. polling), the
processing portion of the current RRQ interrupt handler needs to be broken out
into a separate routine. This will allow RRQ processing from places other than
the RRQ hardware interrupt handler.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>