drm/amd/display: Update hook dcn32_funcs

In DCN32 clk hook functions, we are using the wrong reference for
get_dp_ref_clk_frequency and missing the get_dtb_ref_clk_frequency
reference. This commit adds those references.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>