staging: wfx: fix spelling mistake "non existant" -> "non-existent"

There is a spelling mistake in a dev_warn message. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20191010095748.17047-1-colin.king@canonical.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/hif_rx.c

@@ -137,7 +137,7 @@ static int hif_receive_indication(struct wfx_dev *wdev, struct hif_msg *hif, voi
 	struct hif_ind_rx *body = buf;
 
 	if (!wvif) {
-		dev_warn(wdev->dev, "ignore rx data for non existant vif %d\n", hif->interface);
+		dev_warn(wdev->dev, "ignore rx data for non-existent vif %d\n", hif->interface);
 		return 0;
 	}
 	skb_pull(skb, sizeof(struct hif_msg) + sizeof(struct hif_ind_rx));