drm/amd/pm: Remove min/max overload of pp_dpm_sclk

To maintain consistency with legacy usage, remove min/max clock overload
of pp_dpm_sclk node.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>