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>