scsi: qla2xxx: Flush mailbox commands on chip reset

Flush pending mailbox commands on chip reset.  Wake up command that's
waiting for an interrupt and wait for mailbox counters to go to zero.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>