drm/amd/pp: Remove struct pp_gpu_power

Currently smu only calculate average gpu power in real time.

for vddc/vddci/max power,
User need to set start time and end time, firmware can calculate
the average vddc/vddci/max power. but the type of return values
is not unified. For Vi, return type is uint.
For vega, return type is float.

so this struct can't be suitable for all asics.

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>