video: fbdev: s3c-fb: Mark expected switch fall-throughs

video: fbdev: s3c-fb: Mark expected switch fall-throughs

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

This patch fixes the following warnings:

drivers/video/fbdev/s3c-fb.c: In function ‘s3c_fb_blank’:
drivers/video/fbdev/s3c-fb.c:811:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
   sfb->enabled &= ~(1 << index);
   ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
drivers/video/fbdev/s3c-fb.c:814:2: note: here
  case FB_BLANK_NORMAL:
  ^~~~
  LD [M]  drivers/staging/greybus/gb-light.o
  CC [M]  drivers/gpu/drm/nouveau/nvkm/subdev/secboot/gp10b.o
drivers/video/fbdev/s3c-fb.c: In function ‘s3c_fb_check_var’:
drivers/video/fbdev/s3c-fb.c:286:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
   var->transp.length = 1;
   ~~~~~~~~~~~~~~~~~~~^~~
drivers/video/fbdev/s3c-fb.c:288:2: note: here
  case 18:
  ^~~~
drivers/video/fbdev/s3c-fb.c:314:22: warning: this statement may fall through [-Wimplicit-fallthrough=]
   var->transp.offset = 24;
   ~~~~~~~~~~~~~~~~~~~^~~~
drivers/video/fbdev/s3c-fb.c:316:2: note: here
  case 24:
  ^~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

Notice that, in this particular case, the code comments are modified
in accordance with what GCC is expecting to find.

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>