ath10k: add pdev param support to enable/disable btcoex

10.4 firmware has support to enable or disable btcoex functionality
without reloading firmware via wmi pdev param. Add provision to send
pdev param command via existing btcoex knob.

Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>