UPSTREAM: move d_rcu from overlapping d_child to overlapping d_alias

commit 946e51f2bf37f1656916eb75bd0742ba33983c28 upstream.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Bug: 31856701
Change-Id: I9a7b983408f8f1fd96ce85e940a382ba401d268d
(cherry picked from commit 679829c2)
Signed-off-by: Paul Lawrence <paullawrence@google.com>