fbdev: core: Fix ubsan warning in pixel_to_pat

It could be triggered on 32 bit big endian machines at 32 bpp in the
pattern realignment. In this case just return early as the result is
an identity.

Signed-off-by: Zsolt Kajtar <soci@c64.rulez.org>
Signed-off-by: Helge Deller <deller@gmx.de>

drivers/video/fbdev/core/fb_fillrect.h

@@ -92,8 +92,7 @@ static unsigned long pixel_to_pat(int bpp, u32 color)
 		pattern = pattern | pattern << bpp;
 		break;
 	default:
-		pattern = color;
-		break;
+		return color;
 	}
 #ifndef __LITTLE_ENDIAN
 	pattern <<= (BITS_PER_LONG % bpp);