[ath_hal] add QCA9565 bluteooth antenna control.

This configures the LNA antenna diversity control, which should be on
if wlan owns the LNA for bluetooth coexistence. Otherwise, make sure
it's off.

I think this is eventually intended to allow 1-antenna bluetooth +
wifi setups for QCA9565, but I'm not sure where that's actually configured
in ath9k.

Obtained from: Linux ath9k