drm/amd/display: Fix stream->link_enc unassigned during stream removal

[Why]
Found when running igt@kms_atomic.

Userspace attempts to do a TEST_COMMIT when 0 streams which calls
dc_remove_stream_from_ctx. This in turn calls link_enc_unassign
which ends up modifying stream->link = NULL directly, causing the
global link_enc to be removed preventing further link activity
and future link validation from passing.

[How]
We take care of link_enc unassignment at the start of
link_enc_cfg_link_encs_assign so this call is no longer necessary.

Fixes global state from being modified while unlocked.
Reviewed-by: Jimmy Kizito <Jimmy.Kizito@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -1964,10 +1964,6 @@ enum dc_status dc_remove_stream_from_ctx(
 				dc->res_pool,
 			del_pipe->stream_res.stream_enc,
 			false);
-	/* Release link encoder from stream in new dc_state. */
-	if (dc->res_pool->funcs->link_enc_unassign)
-		dc->res_pool->funcs->link_enc_unassign(new_ctx, del_pipe->stream);
-
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	if (is_dp_128b_132b_signal(del_pipe)) {
 		update_hpo_dp_stream_engine_usage(