drm/amd/display: Refactor DIO stream encoder

* Pull duplicate audio_clock_info struct to stream_encoder.h
* Generalize sec_gsp7* to sec_gsp_pps*
* Expose enc1 and enc2 stream encoder audio funcs

Signed-off-by: Eric Bernstein <eric.bernstein@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>