ath9k: Enable short repeat by default on ath9k_htc

Normal FFT reports generate a LOT of data, to save resources
enable short repeat by default also on ath9k_htc (it's already
enabled by default on ath9k). This can always be changed from
userspace if needed.

Signed-off-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>