scsi: qla2xxx: Add beacon LED config sysfs interface

This patch provides an interface to do the following (using MBC 0x3B):

 - Displays (in hex) the LED config words for all three LEDs.

 - Programs the config words for one LED or for all three LEDs.

The sysfs node defined is named beacon_config.

First, to allow driver to gain LED control, do this:
 # echo 1 > /sys/class/scsi_host/host#/beacon

Then, to display config words for all three LEDs do this:
 # cat /sys/class/scsi_host/host#/beacon_config

To set config words for all three LEDs do this:
 # echo 3 xxxx yyyy zzzz > /sys/class/scsi_host/host#/beacon_config

Or, to set config word for a specific single LED n do this:
 # echo n xxxx > /sys/class/scsi_host/host#/beacon_config
  where n is the LED number (0, 1, 2)

Finally, to restore LED control back to firmware, do this:
 # echo 0 > /sys/class/scsi_host/host#/beacon

Link: https://lore.kernel.org/r/20200212214436.25532-2-hmadhani@marvell.com


Signed-off-by: Joe Carnuccio <joe.carnuccio@cavium.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>