kconfig/nconf: fix compile with ncurses reentrant API

ESCDELAY is a global variable which is replaced by getter and setter
functions with NCURSES_REENTRANT.  This fixes the following error:

nconf.c: In function ‘main’:
nconf.c:1506:2: error: lvalue required as left operand of assignment
Signed-off-by: Yaakov Selkowitz <yselkowitz@users.sourceforge.net>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/nconf.c

@@ -1503,7 +1503,11 @@ int main(int ac, char **av)
 	}
 
 	notimeout(stdscr, FALSE);
+#if NCURSES_REENTRANT
+	set_escdelay(1);
+#else
 	ESCDELAY = 1;
+#endif
 
 	/* set btns menu */
 	curses_menu = new_menu(curses_menu_items);