probe: Improve probe_frid to support both ARM and X86

To unify probing logic, we want to provide a new 'fdt_get_frid' as
equivalent call to `acpi_get_frid`. The `probe_frid` then can
support both X86 and ARM platforms.

BUG=chromium:982692
TEST=emerge-$BOARD mosys

Change-Id: I1d9b86441a1c470946db1c27a72b4e66a305ce7b
Reviewed-on: https://chromium-review.googlesource.com/1697964
Tested-by: Hung-Te Lin <hungte@chromium.org>
Commit-Ready: Hung-Te Lin <hungte@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Hsin-Yi Wang <hsinyi@chromium.org>
3 files changed