carl9170: remove stale rx error path

The total/fatal error bit was erroneously prefixed
with AR9170_RX_ERROR instead of AR9170_RX_STATUS.
Luckily, the hardware specification confirmed that
the 0x80 flag will never be set for mac->error.
So, it was always just a dead branch.

This patch also imports the latest version of
shared wlan.h header from the firmware git.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>