scsi: pm80xx: Fix drives missing during rmmod/insmod loop

scsi: pm80xx: Fix drives missing during rmmod/insmod loop

When driver is loaded after rmmod some drives are not showing up during
discovery.

SATA drives are directly attached to the controller connected phys.  During
device discovery, the IDENTIFY command (qc timeout (cmd 0xec)) is timing out
during revalidation. This will trigger abort from host side and controller
successfully aborts the command and returns success. Post this successful
abort response ATA library decides to mark the disk as NODEV.

To overcome this, inside pm8001_scan_start() after phy_start() call, add get
start response and wait for few milliseconds to trigger next phy start.
This millisecond delay will give sufficient time for the controller state
machine to accept next phy start.

Link: https://lore.kernel.org/r/20210505120103.24497-1-ajish.koshy@microchip.com
Signed-off-by: Ajish Koshy <ajish.koshy@microchip.com>
Signed-off-by: Viswas G <viswas.g@microchip.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>