drm/amdgpu/smu: move fan rpm query into the asic specific code

On vega20, there is an SMU message to query it.  On navi, it's fetched
from the metrics table.

Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
5 files changed