scsi: qla2xxx: Fix NULL pointer crash due to probe failure

scsi: qla2xxx: Fix NULL pointer crash due to probe failure

BugLink: http://bugs.launchpad.net/bugs/1756100
commit d64d6c5671db5e693a0caaee79f2571b098749c9 upstream.

This patch fixes regression added by commit d74595278f4ab
("scsi: qla2xxx: Add multiple queue pair functionality.").

When driver is not able to get reqeusted IRQs from the system, driver will
attempt tp clean up memory before failing hardware probe. During this cleanup,
driver assigns NULL value to the pointer which has not been allocated by
driver yet. This results in a NULL pointer access.

Log file will show following message and stack trace

qla2xxx [0000:a3:00.1]-00c7:21: MSI-X: Failed to enable support, giving up -- 32/-1.
qla2xxx [0000:a3:00.1]-0037:21: Falling back-to MSI mode --1.
qla2xxx [0000:a3:00.1]-003a:21: Failed to reserve interrupt 821 already in use.
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffffc010c4b6>] qla2x00_probe_one+0x18b6/0x2730 [qla2xxx]
PGD 0
Oops: 0002 [#1] SMP

Fixes: d74595278f4ab ("scsi: qla2xxx: Add multiple queue pair functionality.").
Cc: <stable@vger.kernel.org> # 4.10
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>