Add initial support for eMMC layout

Initial commit to add an mmc layout option to update eMMC chips.

Tested: Compiled with each of the three supported options:
        'meson build -Dbmc-layout=<option>' and verified a build/<option>
        subdir was created.

Change-Id: Idfc9c7f0380daff2d865663dacba23c919386d4f
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
5 files changed