ARM: dts: uniphier: add system-bus-controller nodes

The System Bus Controller block has two register regions,
but having only the second one in a separate node was not nice.

Replace it with a new node with two register regions in it.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>