FreeBSD_HEAD - Build #3638 - Fixed

FreeBSD_HEAD - Build #3638 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD/3638/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD/3638/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD/3638/console

Change summaries:

292429 by imp:
Add a generic firmware dependent handle to pass from the loader to the
kernel. This will be used for passing in things like the system table
from EFI or other similar metadata that can be used by the kernel to
communicate with the firmware.

292428 by imp:
No need to test command values this way. There can be only one, even
though the encoding is bit-wise today...

292427 by imp:
Use variable names that aren't as prone to dyslexic confusion.

Suggested by: jmallet_at_

292426 by adrian:
[intrng] Migrate the intrng code from sys/arm/arm to sys/kern/subr_intr.c.

The ci20 port (by kan_at_) is going to reuse almost all of the intrng code
since the SoC in question looks suspiciously like someone took an ARM
SoC design and replaced the ARM core with a MIPS core.

* migrate out the code;
* rename ARM_ -> INTR_;
* rename arm_ -> intr_;
* move the interrupt flush routine from intr.c / intrng.c into
  arm/machdep_intr.c - removing the code duplication and removing
  the ARM specific bits from here.

Thanks to the Star Wars: The Force Awakens premiere line for allowing
me a couple hours of quiet time to finish the universe builds.

Tested:

* make universe

TODO:

* The structure definitions in subr_intr.c still includes machine/intr.h
  which requires one duplicates all of the intrng definitions in
  the platform code (which kan has done, and I think we don't have to.)

  Instead I should break out the generic things (function declarations,
  common intr structures, etc) into a separate header.

* Kan has requested I make the PIC based IPI stuff optional.

292425 by imp:
Scheduling module to introduce a fixed delay into the I/O path.

292424 by imp:
Create a simplebus PNP info wrapper.

Differential Review: https://reviews.freebsd.org/D4517