No other functions use the return value of qlafx00_process_aen() and the
return value is always 0 now. Make it return void. This fixes the following
coccicheck warning:

drivers/scsi/qla2xxx/qla_mr.c:1716:5-9: Unneeded variable: "rval".
Return "0" on line 1768

Link: https://lore.kernel.org/r/20200506061757.19536-1-yanaijie@huawei.comReviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>