uml: set inittab for working console

Signed-off-by: Adrian Panella <ianchi74@outlook.com>

target/linux/uml/base-files/etc/inittab

+# Copyright (c) 2013 The Linux Foundation. All rights reserved.
+::sysinit:/etc/init.d/rcS S boot
+::shutdown:/etc/init.d/rcS K shutdown
+tty0::askfirst:/usr/libexec/login.sh