Pull in recent changes from the main dtc repository. These changes
primarily allow multiple device trees to be declared which are merged
by dtc. This feature allows us to include a basic dts file and then
provide more information for the specific system through the merging
functionality.

Changes pulled from git://git.jdl.com/software/dtc.git
commit id: 37c0b6a0, "dtc: Add code to make diffing trees easier"
Signed-off-by: NJohn Bonesio <bones@secretlab.ca>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>