scsi: qla2xxx: Use a variable for repeated mem_size computation

Use a variable to compute memory size to be allocated once instead of
repeatedly computing it at different locations in the function. Issue
identified using the array_size_dup Coccinelle semantic patch.

Link: https://lore.kernel.org/r/Y7spwF8HTt0c0l7y@ubun2204.myguest.virtualbox.org


Signed-off-by: Deepak R Varma <drv@mailo.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>