drm/amd/display: remove an unnecessary NULL check

The "stream" pointer can't be NULL and it's dereferenced on the line
before so the check doesn't make sense.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -2324,7 +2324,7 @@ static void commit_planes_for_stream(struct dc *dc,
 
 	if ((update_type != UPDATE_TYPE_FAST) && stream->update_flags.bits.dsc_changed)
 		if (top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
-			if (stream && should_use_dmub_lock(stream->link)) {
+			if (should_use_dmub_lock(stream->link)) {
 				union dmub_hw_lock_flags hw_locks = { 0 };
 				struct dmub_hw_lock_inst_flags inst_flags = { 0 };