[Why]
Add support for new fw command for runtime feature detection.

[How]
Driver sends command through ring buffer, and fw returns data back
through this command.
Signed-off-by: Wyatt Wood <wyatt.wood@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Eryk Brol <eryk.brol@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>