arm64: dts: uniphier: add /memreserve/ for spin-table release address

As Documentation/arm64/booting.txt says, the cpu-release-addr
location should be reserved.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>