scsi: pm80xx: Make running_req atomic

scsi: pm80xx: Make running_req atomic

Incorrect value of the running_req was causing the driver unload to be
stuck during the SAS lldd_dev_gone notification handling.  During SATA I/O
completion, for some error status values, the driver schedules the event
handler and running_req is decremented from that.  However, there are some
other error status values (like IO_DS_IN_RECOVERY,
IO_XFER_ERR_LAST_PIO_DATAIN_CRC_ERR) where the I/O has already been
completed by fw/driver so running_req is not decremented.

Also during NCQ error handling, driver itself will initiate READ_LOG_EXT
and ABORT_ALL. When libsas/libata initiate READ_LOG_EXT (0x2F), driver
increments running_req. This will be completed by the driver in
pm80xx_chip_sata_req(), but running_req was not decremented.

Link: https://lore.kernel.org/r/20201102165528.26510-3-Viswas.G@microchip.com.com
Acked-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Signed-off-by: Ruksar Devadi <Ruksar.devadi@microchip.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>