video: fbdev: sh_mobile_lcdcfb: Mark expected switch fall-through

Now that -Wimplicit-fallthrough is passed to GCC by default, the
following warnings shows up:

../drivers/video/fbdev/sh_mobile_lcdcfb.c: In function ‘sh_mobile_lcdc_channel_fb_init’:
../drivers/video/fbdev/sh_mobile_lcdcfb.c:2086:22: warning: this statement may fall
 through [-Wimplicit-fallthrough=]
   info->fix.ypanstep = 2;
   ~~~~~~~~~~~~~~~~~~~^~~
../drivers/video/fbdev/sh_mobile_lcdcfb.c:2087:2: note: here
  case V4L2_PIX_FMT_NV16:
  ^~~~
../drivers/video/fbdev/sh_mobile_lcdcfb.c: In function ‘sh_mobile_lcdc_overlay_fb_init’:
../drivers/video/fbdev/sh_mobile_lcdcfb.c:1596:22: warning: this statement may fall
 through [-Wimplicit-fallthrough=]
   info->fix.ypanstep = 2;
   ~~~~~~~~~~~~~~~~~~~^~~
../drivers/video/fbdev/sh_mobile_lcdcfb.c:1597:2: note: here
  case V4L2_PIX_FMT_NV16:
  ^~~~

Rework to address a warnings due to the enablement of
-Wimplicit-fallthrough.
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
[b.zolnierkie: fix patch summary]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190730152530.3055-1-anders.roxell@linaro.org

drivers/video/fbdev/sh_mobile_lcdcfb.c

@@ -1594,6 +1594,7 @@ sh_mobile_lcdc_overlay_fb_init(struct sh_mobile_lcdc_overlay *ovl)
 	case V4L2_PIX_FMT_NV12:
 	case V4L2_PIX_FMT_NV21:
 		info->fix.ypanstep = 2;
+		/* Fall through */
 	case V4L2_PIX_FMT_NV16:
 	case V4L2_PIX_FMT_NV61:
 		info->fix.xpanstep = 2;
@@ -2084,6 +2085,7 @@ sh_mobile_lcdc_channel_fb_init(struct sh_mobile_lcdc_chan *ch,
 	case V4L2_PIX_FMT_NV12:
 	case V4L2_PIX_FMT_NV21:
 		info->fix.ypanstep = 2;
+		/* Fall through */
 	case V4L2_PIX_FMT_NV16:
 	case V4L2_PIX_FMT_NV61:
 		info->fix.xpanstep = 2;