pds_core: protect devlink callbacks from fw_down state

Don't access structs that have been cleared when in the fw_down
state and the various structs have been cleaned and are waiting
to recover.  This caused a panic on rmmod when already in fw_down
and devlink_param_unregister() tried to check the parameters.

Fixes: 40ced894 ("pds_core: devlink params for enabling VIF support")
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230824161754.34264-2-shannon.nelson@amd.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/amd/pds_core/devlink.c

@@ -10,6 +10,9 @@ pdsc_viftype *pdsc_dl_find_viftype_by_id(struct pdsc *pdsc,
 {
 	int vt;
 
+	if (!pdsc->viftype_status)
+		return NULL;
+
 	for (vt = 0; vt < PDS_DEV_TYPE_MAX; vt++) {
 		if (pdsc->viftype_status[vt].dl_id == dl_id)
 			return &pdsc->viftype_status[vt];