ath9k: Add concurrent WLAN and BT tx support for MCI based chips

This feature enables both WLAN and BT can transmit simultaneously
by setting WLAN and BT to equal priorities. Whenever both are
transmitting, it might violate regulatory power limits. To avoid
regulatory violation, WLAN tx power will be adjusted according to BT
power index based on avaliability of BT scheduling message. If the
combined power exceeds threshold, BT transmission will be held off.

Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>