Bug 1004195 - Add support for device tree in boot.img

Add support for optional device tree image (dt.img)
to boot and recovery images.  Some devices use kernel device
tree and this adds the device tree image as a section within
the boot/recovery images.

Change-Id: Ia783c296e3817a2094c3ea41006f75fe2e2d4d4d
(cherry picked from commit 346a381bf5656083a2d783dc1a9cbc790c934fa9)
Merge pull request #54 from lissyx/bug1004195

Bug 1004195 - Add support for device tree in boot.img r=mwu