ARM: dts: lpc18xx: remove unit addresses from creg childs

DT nodes without reg properties should not have a unit address. This
fixes the following warnings from dtc.

 Warning (unit_address_vs_reg): Node /soc/syscon@40043000/phy@004 has a
 unit name, but no reg property
 Warning (unit_address_vs_reg): Node /soc/syscon@40043000/dma-mux@11c has
 a unit name, but no reg property

Signed-off-by: Joachim Eastwood <manabian@gmail.com>