platsupport: Move default serial definitions

These are moved from libsel4platsupport. They are used in addition to
PS_SERIAL_DEFAULT which is defined in this library, and they also use
interrupt and physical address definitions defined in this library.
Moving them here reduces a bit of indirection when choosing a default
serial device.

pragma once and for all

Fix whitespace

- remove trailing whitespace
- remove duplicate blank lines
- remove blank lines at end of file

fix licenses

pc99: libplatsupport: define IOPort _END constants

Instead of using START + 8, just define the _END of the IO Port range,
so we don't have literals all over the code.