buildroot

linux-firmware: Add missing firmware for the carl9170 driver

For a long time now Atheros USB AR9170 devices have been using the
carl9170 driver which relies on the carl9170-1.fw firmware file.  This
firmware is available in linux-firmware but it wasn't currently
installed by Buildroot.

Signed-off-by: Karoly Pados <kp@tec4data.at>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>