arm: dts: lpc32xx: move USB controller subdevices into own device node

NXP LPC32xx SoC has one USB OTG controller, which is supposed to work
with an external phy (default is NXP ISP1301).

Practically the USB controller contains 5 subdevices:
- host controller   0x3102 0000 -- 0x3102 00FF
- OTG controller    0x3102 0100 -- 0x3102 01FF
- device controller 0x3102 0200 -- 0x3102 02FF
- I2C controller    0x3102 0300 -- 0x3102 03FF
- clock controller  0x3102 0F00 -- 0x3102 0FFF

The USB controller can be considered as a "bus", because the
subdevices above are relatively independent, for example I2C
controller is the same as other two general purpose I2C controllers
found on SoC.

The change is not intended to modify any logic, but it rearranges
existing device nodes, in future it is planned to add a USB clock
controller device node into the same group.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>