MFC: r265238, r265240

Properly free resources in case of error.

CID:		1007032
Found with:	Coverity Prevent(tm)
MFC 262614, 262625, 262626, 262627, 262682, 262714, 262725, 262736

  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.

  Only try to build the static dtb when we're building a static dtb.

  Use proper include path for dtc as well as cpp.

  Fix syntax errors (missing ; other minor glitches) in existing dts files.
MFC: r265583, r265716

First cleanup pass: new sentence -> new line, mdoc, typos and style.

Fix two more typos. (1)

Submitted by:	Trond Endrestol (1)
MFC: r265585

Generate hardware notes for mrsas(4).
MFC r265779:
Fix for NULL pointer.