drm/amd/display: Refactor DSC into component folder

[why]

To refactor DSC and make DSC files unit testable.

[how]

moved the dcnxx_dsc.c and .h files
into corresponding dcn folders inside
the dsc and cleared the linkage errors.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Bhuvana Chandra Pinninti <bhuvanachandra.pinninti@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>