drm/amd/powerplay: remove smu callback funciton get_mclk(get_sclk)

remove smu callback: get_mclk, get_sclk.
because the function smu_get_dpm_freq_range has the same function.

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>