dts: nxp,lpc-gpio: Fix binding to group ports

LPC GPIO binding was wrong in that the reg address
on the simple soc bus was given as an index of the gpio ports
within a gpio controller. Fix this by putting the GPIO node
on the simple bus as a single node with the correct base address,
and make the ports children of this node.

Change the driver to get the port number from the reg address
instead of a custom property, and get base address from DT instead
of the SDK macro definition.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>