[PATCH] fbdev: sh7760fb: document fallthrough cases

Fix fallthrough warnings in sh776fb.c:

../drivers/video/fbdev/sh7760fb.c: In function 'sh7760fb_get_color_info':
../drivers/video/fbdev/sh7760fb.c:138:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
  138 |                 lgray = 1;
../drivers/video/fbdev/sh7760fb.c:143:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
  143 |                 lgray = 1;

Just document the current state of code execution/flow.

Fixes: 4a25e41831ee ("video: sh7760fb: SH7760/SH7763 LCDC framebuffer driver")
Signed-off-by: Randy Dunlap <redacted>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Nobuhiro Iwamatsu <redacted>
Cc: Manuel Lauss <redacted>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
---
 drivers/video/fbdev/sh7760fb.c |    2 ++
 1 file changed, 2 insertions(+)

--- linux-next-20211112.orig/drivers/video/fbdev/sh7760fb.c
+++ linux-next-20211112/drivers/video/fbdev/sh7760fb.c

@@ -136,11 +136,13 @@ static int sh7760fb_get_color_info(struc
 		break;
 	case LDDFR_4BPP_MONO:
 		lgray = 1;
+		fallthrough;
 	case LDDFR_4BPP:
 		lbpp = 4;
 		break;
 	case LDDFR_6BPP_MONO:
 		lgray = 1;
+		fallthrough;
 	case LDDFR_8BPP:
 		lbpp = 8;
 		break;