ARM: kirkwood: refactor dtsi to largest common nodes

Some kirkwood variants (for instance present in the prestera SoCs) do
not have all the peripherals whose nodes are declared in
kirkwood.dtsi. These missing peripherals are SATA, SDIO, and RTC.

As discussed in [1], to avoid that these missing peripherals get
initialized which could result in system hangs when accessing
undocumented/not present HW registers, their corresponding OF nodes
should not get declared at all for some kirkwood variants.

The corresponding OF nodes of these peripherals thus are moved from
kirkwood.dtsi to the kirkwood-628x.dtsi files so that they still are
initialized for these variants where they are present.

[1]
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/167154.html



Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>