drm/amd/powerplay: drop the unnecessary uclk hard min setting

Since soft min setting is enough. Hard min setting is redundant.

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