scsi: lpfc: Correct MDS loopback diagnostics support

The existing MDS loopback diagnostics support processing received frames in
the slowpath work thread. It caps the number of frames it will process at
64, before waiting for another event to indicate additional frame
reception. The net-net is this results in very slow frame processing during
loopback tests and sometimes orphans an io, causing the loopback test to
report failure by the switch.

Move MDS loopback frame processing out of the slow path worker thread and
into the normal RQ processing routines.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>