freebsd_network: Rewrite bus/vm headers to use Haiku phys_addr types directly.

Instead of redeclaring them, which it did so incorrectly on systems
with PAE in some cases. May fix problems on some 32-bit systems.

freebsd_network: Cleanup bustag handling.

* Add an enum with general BUS_SPACE_TAG values for use across platforms.
* Add proper entries for generic IRQs and MSIs and make use of them.

freebsd11_network -> freebsd_network.

FreeBSD 12 has no major changes to the ifnet KPIs that constitute a
source compatibility break, save a single one related to locking
which doesn't really apply to us, and so we don't need to create
a "freebsd12_network" directory to work through the upgrades.