mb/google/rex: Create variant to support ISH enablement

This patch creates a new variant to support the ISH enablement using
Rex platform.The idea here is to leverage the `rex0` code as much as
possible and add specific support for ISH enablement as per the hardware
schematic differences.

BUG=b:284254353
TEST=Able to build google/rex_ish_ec board and boot on target hardware.

Change-Id: I625fd0b31aed998f4e8f2d139827bc212ee8a90b
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75470
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: YH Lin <yueherngl@google.com>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

0 files changed, 0 insertions, 0 deletions