MFC r313982, r314068:
sys: Replace zero with NULL for pointers.

Found with: devel/coccinelle

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Allow BERI virtio-platform code to operate with no PIO devices specified.
We will use it with Bluespec simulator of CHERI processor for invalidating
caches only.

o Switch to use non-mergeable RX buffers to avoid mbuf adjustment needs
o Operate with copy of iov as we expect later it was not modified

Do not configure Altera PIO device on ARM startup.
PIO is a device implemented in soft-core and becomes
available after flashing FPGA only.

Remove dev/virtio/virtio.h include from BERI VirtIO

This header file contains prototypes and defines that only make
sense to the guest VirtIO device drivers.

Reviewed by: br

Eliminate a "cast discards qualifiers" warning when building with gcc.

Add virtio bus 'poll' method allowing us to inform backend we are
going to poll virtqueue.

Use on BERI soft-core to invalidate cpu caches.

Reviewed by: bryanv
Sponsored by: DARPA, AFRL

o Add BERI Virtio Networking Frontend (if_vtbe)
o Move similar block/networking methods to common file
o Follow r275640 and correct MMIO registers width
o Pass value to MMIO platform_note method.

Sponsored by: DARPA, AFRL

o Add PIO and vtblk mmio device info to the tree
o Add FPGA memory window to static dev mappings
o Fix whitespace

Add BERI-specific virtio block backend device driver.
This part intended to operate on ARM side in heterogeneous
(ARM/BERI) system on crystal.

Add BERI-specific virtio mmio "platform" device.
This device provides a connector to Altera PIO allowing us
to interrupt software-implemented virtio mmio backend.

Sponsored by: DARPA, AFRL

Provide a character device allowing us to access BERI memory regions.

Sponsored by: DARPA, AFRL

Add driver for BERI soft processor 'ring buffer' device.
Ring device provides a way for communicate to BERI
peripherals such as BERI debug unit and console.

Sponsored by: DARPA, AFRL