mb/prodrive/atlas: Add support to read from EC EMI

mb/prodrive/atlas: Add support to read from EC EMI

Implement initial support for EMI (Embedded Memory Interface), which
Microchip describes as "a standard run-time mechanism for the system
host to communicate with the Embedded Controller (EC) and other logical
components". EMI allows the host to access regions of EC memory without
requiring any assistance from the EC.

For now, Atlas only uses EMI 0. This change enables EMI 0, subsequent
commits will read data from it.

Change-Id: Ia899ae71e97f9fc259397dfb5fb84ca06545f5d8
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73936
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>