video: Use memset instead of loop

There is a optimized version of memset in u-boot available so use it instead
of the hand written loop version.

Signed-off-by: Matthias Weisser <weisserm@arcor.de>

drivers/video/mb86r0xgdc.c

@@ -77,8 +77,7 @@ static void dsp_init(struct mb86r0x_gdc_dsp *dsp, char *modestr,
 	}
 
 	/* Fill memory with white */
-	for (i = 0; i < var_mode.xres * var_mode.yres / 2; i++)
-		*videomem++ = 0xFFFFFFFF;
+	memset(videomem, 0xFF, var_mode.xres * var_mode.yres * 2);
 
 	mb86r0x.winSizeX = var_mode.xres;
 	mb86r0x.winSizeY = var_mode.yres;