scsi: pm80xx: Add sysfs attribute to track iop0 count

scsi: pm80xx: Add sysfs attribute to track iop0 count

A new sysfs variable 'ctl_iop0_count' is being introduced that tells if
the controller is alive by indicating controller ticks. If on subsequent
run we see the ticks changing that indicates that controller is not
dead.

Using the 'ctl_iop0_count' sysfs variable we can see ticks incrementing:

    linux-9saw:~# cat /sys/class/scsi_host/host*/ctl_iop0_count
    0x000000a3
    0x000001db
    0x000001e4
    0x000001e7

Link: https://lore.kernel.org/r/20210415103352.3580-5-Viswas.G@microchip.com
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Vishakha Channapattan <vishakhavc@google.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Signed-off-by: Ruksar Devadi <Ruksar.devadi@microchip.com>
Signed-off-by: Ashokkumar N <Ashokkumar.N@microchip.com>
Signed-off-by: Radha Ramachandran <radha@google.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>