arm: omap5: secure API for EMIF memory reservations

Create a few public APIs which rely on secure world ROM/HAL
APIs for their implementation. These are intended to be used
to reserve a portion of the EMIF memory and configure hardware
firewalls around that region to prevent public code from
manipulating or interfering with that memory.

Signed-off-by: Daniel Allred <d-allred@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>