drm/qxl: prevent memory leak

The allocated memory for qdev->dumb_heads should be released
in qxl_destroy_monitors_object before qxl suspend.
otherwise,qxl_create_monitors_object will be called to
reallocate memory for qdev->dumb_heads after qxl resume,
it will cause memory leak.

Signed-off-by: Zongmin Zhou <zhouzongmin@kylinos.cn>
Link: https://lore.kernel.org/r/20230801025309.4049813-1-zhouzongmin@kylinos.cn
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>

Author: Zongmin Zhou

drivers/gpu/drm/qxl/qxl_display.c

@@ -1229,6 +1229,9 @@ int qxl_destroy_monitors_object(struct qxl_device *qdev)
 	if (!qdev->monitors_config_bo)
 		return 0;
 
+	kfree(qdev->dumb_heads);
+	qdev->dumb_heads = NULL;
+
 	qdev->monitors_config = NULL;
 	qdev->ram_header->monitors_config = 0;