ath9k_htc: advertise support for TDLS

ath9k_htc: advertise support for TDLS

Based on a quick test with AR9271, TDLS seems to be working fine.

Tests were done with 2 Atheros AR9271 based devices with firmware
1.3 (sha1 8d49f928aa40ac53c729189bff1333cd373a7fb5), associated
with a WAP54G access point. TDLS worked fine both in WPA2 mode and
without encryption. Stations maintained ping flood traffic between
each other and towards the AP without significant losses.

Not tested with AR7010.

TDLS was enabled in earlier patches the same way for other
Atheros drivers:
ath9k (fd6562344dea2b8b2a5d644cf971f4e56004500a),
and carl9170 (d1f3de71a584a82ee4e84505fce9acccf40215ff).

Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>