drm/amd/pm: remove the average clock value in sysfs

if it's fine-grained clock dpm, remove the average clock value and
reflects the real clock.

Signed-off-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>