OMAP: DSS2: remove non-zero check on variable r

Variable r is being initialized to zero, so the check of a non-zero
rv is redundant and can be removed.

It appears that the previous case statements set r to be -EINVAL
and the "Fallthrough" comment afterwards suggested it was going
to fall through to this non-zero check but won't because of the
break statement. Remove the confusion by removing the Fallthrough
comment too.

Addresses-Coverity: ("Logically dead code")
Fixes: b39a982d ("OMAP: DSS2: omapfb driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191204152847.1435188-1-colin.king@canonical.com

drivers/video/fbdev/omap2/omapfb/omapfb-main.c

@@ -1154,16 +1154,12 @@ static int _setcolreg(struct fb_info *fbi, u_int regno, u_int red, u_int green,
 		   r = fbdev->ctrl->setcolreg(regno, red, green, blue,
 		   transp, update_hw_pal);
 		   */
-		/* Fallthrough */
 		r = -EINVAL;
 		break;
 	case OMAPFB_COLOR_RGB565:
 	case OMAPFB_COLOR_RGB444:
 	case OMAPFB_COLOR_RGB24P:
 	case OMAPFB_COLOR_RGB24U:
-		if (r != 0)
-			break;
-
 		if (regno < 16) {
 			u32 pal;
 			pal = ((red >> (16 - var->red.length)) <<