video: fbdev: cirrusfb: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Notice that in this particular case I placed the "fall through" comment
on its own line, which is what GCC is expecting to find.
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/cirrusfb.c

@@ -1477,10 +1477,12 @@ static void init_vgachip(struct fb_info *info)
 		mdelay(100);
 		/* mode */
 		vga_wgfx(cinfo->regbase, CL_GR31, 0x00);
-	case BT_GD5480:  /* fall through */
+		/* fall through */
+	case BT_GD5480:
 		/* from Klaus' NetBSD driver: */
 		vga_wgfx(cinfo->regbase, CL_GR2F, 0x00);
-	case BT_ALPINE:  /* fall through */
+		/* fall through */
+	case BT_ALPINE:
 		/* put blitter into 542x compat */
 		vga_wgfx(cinfo->regbase, CL_GR33, 0x00);
 		break;