Add unpackbootimg.
mkbootimg: Add --dt parameter to specify DT image

New optional --dt parameter to specify a kernel device
tree image.

Change-Id: I7e2c48c25c04165642eedadc3dc16a082dd99eb0

Conflicts:
	mkbootimg/mkbootimg.c

Conflicts:
	mkbootimg/mkbootimg.c
unpackbootimg: Add support for device trees

Change-Id: I340eed99d2274a2f4cbaf5a9f27726ff3a9302e5