i40e: avoid null pointer dereference

i40e: avoid null pointer dereference

Orabug: 24568124

In function i40e_debug_aq parameter desc is assumed to be
possibly NULL. Do not dereference it before checking the
value.

Fixes: f905dd62be88 ("i40e/i40evf: add max buf len to aq debug print helper")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit cd956722167ba4fdba9c1ce3eed251b04ea2e10f)
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>