[DRIVERS] i.MX: add low level support for i.MX serial port.

This only adds the required i.MX support to get it working in
polling mode at Xvisor startup.

More complete support will be added later.

Signed-off-by: Anup Patel <anup@brainfault.org>
[ARM] i.MX: Add AVIC interrupt controller support.

Signed-off-by: Anup Patel <anup@brainfault.org>
[ARM] i.MX: Add EPIT timer support.

Signed-off-by: Anup Patel <anup@brainfault.org>
[ARM] i.MX: Add i.MX31 support and KZM boad support

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