iwlwifi: avoid crash on unsupported debug collection

If the opmode doesn't support debug collection (DVM) then don't
crash, but just skip the callback.

Fixes: d0129315 ("iwlwifi: dbg: add op_mode callback for collecting debug data.")
Reported-by: Andy Lavr <andy.lavr@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210219133506.ecabe285bc7d.I73d230d555c595fa2d9bf284f80078729fe18aa4@changeid

drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h

@@ -205,6 +205,8 @@ static inline void iwl_op_mode_time_point(struct iwl_op_mode *op_mode,
 					  enum iwl_fw_ini_time_point tp_id,
 					  union iwl_dbg_tlv_tp_data *tp_data)
 {
+	if (!op_mode || !op_mode->ops || !op_mode->ops->time_point)
+		return;
 	op_mode->ops->time_point(op_mode, tp_id, tp_data);
 }