scsi: qla2xxx: Fix flash update in 28XX adapters on big endian machines

Flash update failed due to missing endian conversion in FLT region access
as well as in checksum computation.

Link: https://lore.kernel.org/r/20201202132312.19966-12-njavali@marvell.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>