ath10k: add thermal cooling device support

Thermal cooling device support is added to control the temperature
by throttling the data transmission for the given duration. Throttling
is done using hw MAC quiet time setting. Period, duration and offset
from TBTT can be set up to quiet the MAC transmits for the required duty
cycle (% of quiet duration). The thermal device allows user to configure
duty cycle.

The quiet params are derived as follows.
	period = max(25TU, beacon interval / number of bss)
	duration = period * duty cycle / 100

Quiet mode can be disabled by setting the duty cycle to 0. The cooling
device can be found under /sys/class/thermal/cooling_deviceX/.
Corresponding soft link to this device can be found under phy folder.

/sys/class/ieee80211/phy*/device/cooling_device.

To set duty cycle as 40%,

echo 40 >/sys/class/ieee80211/phy*/device/cooling_device/cur_state

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