drm/amd/amdgpu_dm/mst: Remove ->destroy_connector() callback

Pankaj Bharadiya started cleaning up the MST connector callbacks a while
ago, as I pointed out that they are the same across every driver and
don't serve much purpose. There was one callback that was left over
though from amdgpu, that we delayed removing due to not being completely
sure as to whether or not it was needed.

So, I've read through said callback and can confirm it's not at all
needed. Pretty much all of the work that is done in
dm_dp_destroy_mst_connector() can be done in
dm_dp_mst_connector_destroy(). Additionally, I've removed some bits that
didn't actually do anything:

* Removed DRM_INFO message we were printing, this shouldn't be info
  level and there's more appropriate drm debugging flags that should be
  used instead
* Removed amdgpu_dm_update_freesync_caps() - reading into this function,
  it doesn't actually do anything important and I'm not sure why it was
  ever being called here
* Stop clearing aconnector->dc_sink - this also doesn't do anything
* Stop clearing link settings in dc_link - this also doesn't do anything
* Also, use shorter variable

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200331205740.135525-3-lyude@redhat.com


Reviewed-by: Alex Deucher <alexdeucher@gmail.com>