video: ipu_disp: Return a negative value on error

We should return a negative error number (-EINVAL) on error.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>

drivers/video/ipu_disp.c

@@ -889,7 +889,7 @@ int32_t ipu_init_sync_panel(int disp, uint32_t pixel_clk,
 	debug("panel size = %d x %d\n", width, height);
 
 	if ((v_sync_width == 0) || (h_sync_width == 0))
-		return EINVAL;
+		return -EINVAL;
 
 	adapt_panel_to_ipu_restricitions(&pixel_clk, width, height,
 					 h_start_width, h_end_width,