drm/amd/display: Show the DCN/DCE version in the log

Some times people send their dmesg log for debugging, and one common
task is to check the modesetting line to catch which DCN/DCE we need to
debug. This commit introduces a simple conversion from the DCN/DCE
version to a string shown in the dmesg log.

Reviewed-by: Hamza Mahfooz <Hamza.Mahfooz@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>