carl9170: advertise support for TDLS

Based on a quick test [ath9k and carl9170],
TDLS seemed to be working fine. And while
we are at it, let's move the wiphy feature
flag set from carl9170_alloc into a single
place in carl9170_fw.

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