On some boards the rpm interface apparently does not work at all
leading to the fan not spinning or spinning at strange speeds.
Both interfaces work properly on the boards I have.
Let's try and use the percent interface instead.

v2: rebase on revert

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1408
Reviewed-by: Evan Quan <evan.quan@amd.com> (v1)
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>