drm/radeon: Don't unreserve twice on failure to validate.

This is done later in radeon_object_list_unvalidate(). Doing it twice triggers
a BUG in TTM, rendering X on KMS unusable until reboot.
Signed-off-by: Michel Dänzer <daenzer@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_object.c

@@ -433,7 +433,6 @@ int radeon_object_list_validate(struct list_head *head, void *fence)
 						       robj->tobj.proposed_placement,
 						       true, false);
 			if (unlikely(r)) {
-				radeon_object_list_unreserve(head);
 				DRM_ERROR("radeon: failed to validate.\n");
 				return r;
 			}