[why]
Move DCN3X files to unique component folder.

[how]
Create respective component folder in dc, move the DCN3X files into
corresponding new folders and made appropriate changes for compilation
in Makefiles.
Reviewed-by: Martin Leung <martin.leung@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Mounika Adhuri <moadhuri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>