drm/amd/powerplay: get bootup fclk value

This is available with firmwareinfo table v3.2 or later.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>