Revert "drm/amdgpu/swsmu: drop set_fan_speed_percent (v2)"

On some boards the rpm interface apparently does not work at all
leading to the fan not spinning or spinning at strange speeds.
Revert this for now to fix 5.10, 5.11.  The follow on patch
fixes this properly for 5.12.

This reverts commit 8d6e65ad.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1408


Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org