carl9170 firmware: update README

the README should include a list of all necessary
tools and libraries to build the firmware.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>

carl9170 firmware: checkpatch fixes

Since the shared headers are meant to be included
into the kernel, they should pass checkpatch.pl
without generating hundreds of WARNINGS.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>

carl9170 firmware: import 1.7.0

The carl9170 project aims to provide more than just a
working substitute firmware+driver for Atheros' AR9170
USB solutions.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>