Add Virtio MMIO bus driver.

Sponsored by:	DARPA, AFRL


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274655 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Add Altera Parallel IO (PIO) device driver.

Sponsored by:	DARPA, AFRL


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274656 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f