drm/amdgpu/powerplay/smu7: drop refresh rate checks for mclk switching

The logic has moved to cgs.  mclk switching with DC at higher refresh
rates should work.

Reviewed-by: Eric Huang <JinhuiEric.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>