mainboard/google/reef: allow variants to modify nhlt oem revision

In order to mirror the full flexibility of the NHLT library that
allows a caller to set the OEM revision field in the ACPI header
modify the variant callback to override the value.

Change-Id: I16e539b350a50e3c163be1439c8637b82e53a759
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17651
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
2 files changed