carl9170 firmware: investigate 80/88MHz clock freezes

The SoC can run up to 80/88MHz in HT40 mode. This improves
throughput and timing accuracy over the 40/44MHz clock.
However some devices seem to become unstable under load.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
carl9170 toolchain: update to gcc-4.9.1

For users with issues due to a gcc-4.9 host compiler:
<https://bugzilla.redhat.com/show_bug.cgi?id=1087374>

Note: The README.md has been updated as well. For
requests about the firmware (or driver) please
include "carl9170" in the subject line.

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