[CORE] vmm_main: Add API to check whether system init is complete

This patch add vmm_init_done() API to check whether system init
is complete or not.

Signed-off-by: Anup Patel <anup@brainfault.org>
[DAEMONS] mterm: Sleep if system initialization not complete

It might happen that system workqueue sleeps for some event and
mterm starts executing even before system is initialized hence
this patch using vmm_init_done() and vmm_msleep() APIs to sleep
untill system is initialized. If we don't do this then mterm
prints will overlap the system initialization prints.

Signed-off-by: Anup Patel <anup@brainfault.org>