ath9k: enable hw manual peak calibration for QCA9561

This patch fix https://lists.openwrt.org/pipermail/openwrt-devel/


2015-August/034979.html. As the peak detect calibration is set
incorrectly.

Signed-off-by: Miaoqing Pan <miaoqing@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>