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

Integrate device-tree upstream files into the build process:
(1) Invoke cpp to bring in files via #include (although the old
/include/ stuff is supported still).
(2) bring in files from either vendor tree or freebsd-custom files
when building.
(3) move all dts* files from sys/boot/fdt/dts to
sys/boot/fdt/dts/${MACHINE} as appropriate.
(4) encode all the magic to do the build in sys/tools/fdt/make_dtb.sh
so that the different places in the tree use the exact same logic.
(5) switch back to gpl dtc by default. the bsdl one in the tree has
significant issues not easily addressed by those unfamiliar with
the code.

- Pin configuration is a complete iomux register now and includes
drive strength, pull mode, mux mode, speed, etc.
- Add i2c devices to the tree
- Add IPG clock

o Expand device tree information
o Export iomuxc (pins) configuration to DTS
o Allow devices to assign clocks in DTS

Add support for Freescale Vybrid Family VF600 heterogeneous
ARM Cortex-A5/M4 SoC (M4 core is not used in this work).

Support includes device drivers for:
- NAND Flash Controller (NFC)
- USB Enhanced Host Controller Interface (EHCI)
- General-Purpose Input/Output (GPIO)
- Universal Asynchronous Receiver/Transmitter (UART)

Also supported:
- Generic Interrupt Controller (GIC)
- MPCore timer
- ffec ethernet driver

Reviewed by: ray
Approved by: cognet (mentor)