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

As <machine/pmap.h> is included from <vm/pmap.h>, there is no need to
include it explicitly when <vm/pmap.h> is already included.

Reviewed by: alc, kib
Differential Revision: https://reviews.freebsd.org/D5373

Convert rman to use rman_res_t instead of u_long

Summary:
Migrate to using the semi-opaque type rman_res_t to specify rman resources. For
now, this is still compatible with u_long.

This is step one in migrating rman to use uintmax_t for resources instead of
u_long.

Going forward, this could feasibly be used to specify architecture-specific
definitions of resource ranges, rather than baking a specific integer type into
the API.

This change has been broken out to facilitate MFC'ing drivers back to 10 without
breaking ABI.

Reviewed By: jhb
Sponsored by: Alex Perez/Inertial Computing
Differential Revision: https://reviews.freebsd.org/D5075

Remove more unused variables leading to compile time errors.

Add domain support to PCI bus allocation

When the system has more than a single PCI domain, the bus numbers
are not unique, thus they cannot be used for "pci" device numbering.
Change bus numbers to -1 (i.e. to-be-determined automatically)
wherever the code did not care about domains.

Reviewed by: jhb
Obtained from: Semihalf
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3406

Reshuffle all of the DDR flush operations into a single switch/mux,
and start teaching subsystems about it.

The Atheros MIPS platforms don't guarantee any kind of FIFO consistency
with interrupts in hardware. So software needs to do a flush when it
receives an interrupt and before it calls the interrupt handler.

There are new ones for the QCA934x and QCA955x, so do a few things:

* Get rid of the individual ones (for ethernet and IP2);
* Create a mux and enum listing all the variations on DDR flushes;
* replace the uses of IP2 with the relevant one (which will typically
be "PCI" here);
* call the USB DDR flush before calling the real USB interrupt handlers;
* call the ethernet one upon receiving an interrupt that's for us,
rather than never calling it during operation.

Tested:

* QCA9558 (TP-Link archer c7 v2)
* AR9331 (Carambola 2)

TODO:

* PCI, USB, ethernet, etc need to do a double-check to see if the
interrupt was truely for them before doing the DDR. For now I
prefer "correct" over "fast".

Add initial support for the QCA955x PCIe host controller.

The QCA955x looks a lot like the AR724x PCIe controller, except it
supports two root complexes. Unfortunately I only have one, so
although this code has started down the path of supporting more than
one, it's definitely not yet ready.

Tested:

* AP135 board (QCA9558 SoC), with the 11ac NIC swapped for an AR9380
PCIe NIC.

Notes:

* Yes, this driver isn't very pretty. I decided to commit what I have
versus holding onto something that isn't yet finished. It is enough
to bring up the above NIC and interrupt routing works, so it's a good
start.

* However, yes, the DDR flush routine hooks need to be fixed up.
I don't think I'm firing the right one at the moment.