drm/stm: ltdc: use DRM_WARN for fifo & transfer error messages

Use DRM_WARN() instead of DRM_DEBUG_DRIVER() to better
inform the user in case of fifo underruns or
transfer errors.
Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
Acked-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1553874548-31366-1-git-send-email-yannick.fertre@st.com

drivers/gpu/drm/stm/ltdc.c

@@ -822,11 +822,11 @@ static void ltdc_plane_atomic_update(struct drm_plane *plane,
 
 	mutex_lock(&ldev->err_lock);
 	if (ldev->error_status & ISR_FUIF) {
-		DRM_DEBUG_DRIVER("Fifo underrun\n");
+		DRM_WARN("ltdc fifo underrun: please verify display mode\n");
 		ldev->error_status &= ~ISR_FUIF;
 	}
 	if (ldev->error_status & ISR_TERRIF) {
-		DRM_DEBUG_DRIVER("Transfer error\n");
+		DRM_WARN("ltdc transfer error\n");
 		ldev->error_status &= ~ISR_TERRIF;
 	}
 	mutex_unlock(&ldev->err_lock);