kconfig: fix the rule of mainmenu_stmt symbol

The rule of mainmenu_stmt does not have debug print of zconf_lineno(),
but if it had, it would print a wrong line number for the same reason
as commit b2d00d7c61 ("kconfig: fix line numbers for if-entries in
menu tree").

The mainmenu_stmt does not need to eat following empty lines because
they are reduced to common_stmt.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/zconf.y

@@ -31,7 +31,7 @@ struct symbol *symbol_hash[SYMBOL_HASHSIZE];
 static struct menu *current_menu, *current_entry;
 
 %}
-%expect 31
+%expect 30
 
 %union
 {
@@ -117,7 +117,7 @@ start: mainmenu_stmt stmt_list | stmt_list;
 
 /* mainmenu entry */
 
-mainmenu_stmt: T_MAINMENU prompt nl
+mainmenu_stmt: T_MAINMENU prompt T_EOL
 {
 	menu_add_prompt(P_MENU, $2, NULL);
 };