video: fbdev: tridentfb: remove deadcode on unreachable case statement

The value of tmp being used in the switch statement has the range of
just 0..3 hence the case 4 statement can never be reached and is
deadcode and can be removed.

Detected by CoverityScan, CID#744384 ("Logically dead code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/tridentfb.c

@@ -777,9 +777,6 @@ static int get_nativex(struct tridentfb_par *par)
 	case 3:
 		x = 800; y = 600;
 		break;
-	case 4:
-		x = 1400; y = 1050;
-		break;
 	case 1:
 	default:
 		x = 640;  y = 480;