drm/amd/display: Fix writeback_info is not removed

[WHY]
Counter j was not updated to present the num of writeback_info when
writeback pipes are removed.

[HOW]
update j (num of writeback info) under the correct condition.
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -516,11 +516,12 @@ bool dc_stream_remove_writeback(struct dc *dc,
 			if (stream->writeback_info[i].dwb_pipe_inst == dwb_pipe_inst)
 				stream->writeback_info[i].wb_enabled = false;
 
-			if (j < i)
-				/* trim the array */
+			/* trim the array */
+			if (j < i) {
 				memcpy(&stream->writeback_info[j], &stream->writeback_info[i],
 						sizeof(struct dc_writeback_info));
-			j++;
+				j++;
+			}
 		}
 	}
 	stream->num_wb_info = j;