Small cleanup of memory resource allocation from Cambria branch:

Small cleanup of memory resource allocation from Cambria branch:
o encode need for A4 bus space tag hackery according to the memory
  address; checking for "uart" breaks down with the GPS chip support
  which is also a uart but does not require the same hackery
o encode the correct memory window instead of carving up all of i/o
  space, potentially with a larger window than a device should have;
  this likely should be handled in the drivers by using a proper bus
  alloc call but since some drivers depend on the bus support to figure
  this out we cannot simply mod them
o add optional GPS and RS485 support (conditionally as the support
  isn't ready yet)