[WHAT]
Group the FreeSync/VRR helpers from amdgpu_dm.c into a dedicated
amdgpu_dm_freesync.c and amdgpu_dm_freesync.h. The moved functions are:

  is_dc_timing_adjust_needed, is_timing_unchanged_for_freesync,
  set_freesync_fixed_config, reset_freesync_config_for_crtc,
  get_freesync_config_for_crtc, update_freesync_state_on_stream,
  update_stream_irq_parameters, amdgpu_dm_handle_vrr_transition.

The FreeSync/VRR helpers exposed by amdgpu_dm_freesync.h are called
from amdgpu_dm.c, so give the seven that lacked a namespace prefix the
standard amdgpu_dm_ prefix:

Relocate the corresponding KUnit tests into amdgpu_dm_freesync_test.c.

No functional change.

Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>