drm/amd/display: Should disable when new stream is null

core_link_disable_stream should be called when the new stream is null
(i.e. want to disable). Modify the if condition to reflect that.
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -1868,8 +1868,10 @@ static void dce110_reset_hw_ctx_wrap(
 				pipe_need_reprogram(pipe_ctx_old, pipe_ctx)) {
 			struct clock_source *old_clk = pipe_ctx_old->clock_source;
 
-			/* disable already, no need to disable again */
-			if (pipe_ctx->stream && !pipe_ctx->stream->dpms_off)
+			/* Disable if new stream is null. O/w, if stream is
+			 * disabled already, no need to disable again.
+			 */
+			if (!pipe_ctx->stream || !pipe_ctx->stream->dpms_off)
 				core_link_disable_stream(pipe_ctx_old, FREE_ACQUIRED_RESOURCE);
 
 			pipe_ctx_old->stream_res.tg->funcs->set_blank(pipe_ctx_old->stream_res.tg, true);