We need to add "clean-files" in Makfiles to clean up DT blobs, but we
often miss to do so.

Since there are no source files that end with .dtb or .dtb.S, so we
can clean-up those files from the top-level Makefile.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NRob Herring <robh@kernel.org>

Place northstar2 into its own subdirectory.  This helps as the number
of Broadcom boards grow and we can separate them per SoC.
Signed-off-by: NScott Branden <scott.branden@broadcom.com>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>