drm/amd/powerplay: separate Polaris fan table setup from Tonga

Instead of sharing the fan table setup with Tonga, Polaris has
its own fan table setup.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>