kconfig: annotate non-trivial fall-trough

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>
diff --git a/scripts/kconfig/gconf.c b/scripts/kconfig/gconf.c
index a11d5f7..c406bde 100644
--- a/scripts/kconfig/gconf.c
+++ b/scripts/kconfig/gconf.c
@@ -1172,6 +1172,7 @@
 			row[COL_BTNVIS] = GINT_TO_POINTER(TRUE);
 		if (sym_is_choice(sym))
 			break;
+		/* fall through */
 	case S_TRISTATE:
 		val = sym_get_tristate_value(sym);
 		switch (val) {