drm/amd/amdgpu: fix refcount leak

[Why]
the gem object rfb->base.obj[0] is get according to num_planes
in amdgpufb_create, but is not put according to num_planes

[How]
put rfb->base.obj[0] in amdgpu_fbdev_destroy according to num_planes

Signed-off-by: Jingwen Chen <Jingwen.Chen2@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_fb.c

@@ -288,10 +288,13 @@ static int amdgpufb_create(struct drm_fb_helper *helper,
 static int amdgpu_fbdev_destroy(struct drm_device *dev, struct amdgpu_fbdev *rfbdev)
 {
 	struct amdgpu_framebuffer *rfb = &rfbdev->rfb;
+	int i;
 
 	drm_fb_helper_unregister_fbi(&rfbdev->helper);
 
 	if (rfb->base.obj[0]) {
+		for (i = 0; i < rfb->base.format->num_planes; i++)
+			drm_gem_object_put(rfb->base.obj[0]);
 		amdgpufb_destroy_pinned_object(rfb->base.obj[0]);
 		rfb->base.obj[0] = NULL;
 		drm_framebuffer_unregister_private(&rfb->base);