scsi: qla2xxx: Fix incorrect region-size setting in optrom SYSFS routines

Commit e6f77540 ("scsi: qla2xxx: Fix an integer overflow in sysfs
code") incorrectly set 'optrom_region_size' to 'start+size', which can
overflow option-rom boundaries when 'start' is non-zero.  Continue setting
optrom_region_size to the proper adjusted value of 'size'.

Fixes: e6f77540 ("scsi: qla2xxx: Fix an integer overflow in sysfs code")
Cc: stable@vger.kernel.org
Signed-off-by: Andrew Vasquez <andrewv@marvell.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>