vt: annotate implicit fall throughs

There is a plan to build the kernel with -Wimplicit-fallthrough and
these places in the code produced warnings (W=1). Fix them up.

This commit remove the following warning:

  drivers/tty/vt/vt.c:2112:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
  drivers/tty/vt/vt.c:2237:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/vt/vt.c

@@ -2111,6 +2111,7 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
 		lf(vc);
 		if (!is_kbd(vc, lnm))
 			return;
+		/* fall through */
 	case 13:
 		cr(vc);
 		return;
@@ -2236,6 +2237,7 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
 		vc->vc_ques = (c == '?');
 		if (vc->vc_ques)
 			return;
+		/* fall through */
 	case ESgetpars:
 		if (c == ';' && vc->vc_npar < NPAR - 1) {
 			vc->vc_npar++;