video/omap: remove invalid check

regno is unsigned so it cannot be negative.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576Signed-off-by: NAndrzej Hajda <a.hajda@samsung.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/fbdev/omap/omapfb_main.c

@@ -276,11 +276,6 @@ static int _setcolreg(struct fb_info *info, u_int regno, u_int red, u_int green,
 		if (r != 0)
 			break;
 
-		if (regno < 0) {
-			r = -EINVAL;
-			break;
-		}
-
 		if (regno < 16) {
 			u16 pal;
 			pal = ((red >> (16 - var->red.length)) <<