drm/amd/display: Use DCN2 functions instead of DCE

[WHY]
DCN code should make as few references to DCE as possible

[HOW]
Copy DCE110 implementation of find_first_free_match_stream_enc_for_link
into DCN10

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>