Revert "drm/amd/powerply: fix power reading on Fiji"

we don't have limit of [50ms, 4sec] sampling period.
smu calculate average gpu power in real time.
we can read average gpu power through smu message or
read special register.

This reverts commit 462d8dcc9fec0d89f1ff6a1f93f1d4f670878c71.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>