This imports the tools/include dir from the Kernel as of 4.5-rc1 to
barebox.
The Kernel has many useful defines and helpers which are often
duplicated in the different tools. Let's create a copy of them
in a common place for all tools.

Some files have been skipped for now as I currently see no use for them:

include/linux/filter.h
include/linux/hash.h
include/linux/rbtree.h
include/linux/rbtree_augmented.h

They can be added later if needed.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>