In case of IOCB Queue full or system where memory is low and driver
receives large number of RSCN storm, the stale sp pointer can stay on
gpnid_list resulting in page_fault.

This patch fixes this issue by initializing the sp->elem list head and
removing sp->elem before memory is freed.

Following stack trace is seen

 9 [ffff987b37d1bc60] page_fault at ffffffffad516768 [exception RIP: qla24xx_async_gpnid+496]
10 [ffff987b37d1bd10] qla24xx_async_gpnid at ffffffffc039866d [qla2xxx]
11 [ffff987b37d1bd80] qla2x00_do_work at ffffffffc036169c [qla2xxx]
12 [ffff987b37d1be38] qla2x00_do_dpc_all_vps at ffffffffc03adfed [qla2xxx]
13 [ffff987b37d1be78] qla2x00_do_dpc at ffffffffc036458a [qla2xxx]
14 [ffff987b37d1bec8] kthread at ffffffffacebae31

Fixes: 2d73ac61 ("scsi: qla2xxx: Serialize GPNID for multiple RSCN")
Cc: <stable@vger.kernel.org> # v4.17+
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>