ARM: dts: lpc18xx: remove skeleton.dtsi include and fix unit address warnings

Removale of skeleton.dtsi allows us also to fix the following
warning from the dts compiler:
  Warning (unit_address_vs_reg): Node /memory has a reg or ranges property, but no unit name

by adding proper unit addresses to the memory nodes.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>