drm/amd/powerplay: add control method to bypass metrics cache on Navi10

As for the gpu metric export, metrics cache makes no sense. It's up to
user to decide how often the metrics should be retrieved.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>