Change removing a LUN using sysfs from an internal driver function
pqi_remove_all_scsi_devices() to using the .slave_destroy entry in the
scsi_host_template.

A LUN can be deleted via sysfs using this syntax:

echo 1 > /sys/block/sdX/device/delete

Link: https://lore.kernel.org/r/165730607154.177165.9723066932202995774.stgit@brunhildaReviewed-by: NScott Teel <scott.teel@microchip.com>
Reviewed-by: NMike McGowen <mike.mcgowen@microchip.com>
Signed-off-by: NKevin Barnett <kevin.barnett@microchip.com>
Signed-off-by: NDon Brace <don.brace@microchip.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>