ath9k_hw: move ath_extend_tsf() to hw code to share as ath9k_hw_extend_tsf()

This will be shared between ath9k and ath9k_htc.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --cc drivers/net/wireless/ath/ath9k/hw.c
Simple merge

diff --cc drivers/net/wireless/ath/ath9k/hw.h
Simple merge

diff --cc drivers/net/wireless/ath/ath9k/recv.c
Simple merge