- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Add AR9341, AR9342, AR9344 SoC types.

* Add AR9330/AR9331 to the soc identifier enum;
* Set it when probing the CPU type.

Preparation work for supporting the AR91xx and AR724x.

* Implement a SoC probe function, from Linux, which determines the
SoC family, type and revision. This only probes the AR71xx series
SoC and (currently) panics on others.

* Migrate some of the AR71XX specific hardware init (USB device, determining
system frequencies) into using the cpuops introduced in an earlier commit.
Other SoC specific hardware stuff (per-device flush/WB, GPIO pin wiring,
Ethernet PLL setup, other things I've likely missed) will be introduced in
subsequent commits.

Reviewed by: imp@
Obtained from: (partially) Linux