video: fbdev: sm501fb: mark expected switch fall-through in sm501fb_blank_crt

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

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/sm501fb.c

@@ -1008,6 +1008,7 @@ static int sm501fb_blank_crt(int blank_mode, struct fb_info *info)
 	case FB_BLANK_POWERDOWN:
 		ctrl &= ~SM501_DC_CRT_CONTROL_ENABLE;
 		sm501_misc_control(fbi->dev->parent, SM501_MISC_DAC_POWER, 0);
+		/* fall through */
 
 	case FB_BLANK_NORMAL:
 		ctrl |= SM501_DC_CRT_CONTROL_BLANK;