scsi: megaraid_sas: Add watchdog thread to detect Firmware fault

Currently driver checks for Firmware state change from ISR context, and
only when there are interrupts tied with no I/O completions.  We have seen
multiple cases where doorbell interrupts sent by firmware to indicate FW
state change are not processed by driver and it takes long time for driver
to trigger OCR. And if there are no IOs running, since we only check the FW
state as part of ISR code, fault goes undetected by driver and OCR will not
be triggered.

This patch introduces a separate workqueue that runs every one second to
detect Firmware FAULT state and trigger reset immediately.  As an
additional gain, removing PCI reads from ISR to check FW state results in
improved performance as well.

Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>