ath10k: Add support to read btcoex related data from DT

BTCOEX feature is not supported by all QCA4019 chipsets.
Since btcoex enabled by default in firmware, host needs to
enable COEX support depends on the hardware. Enabling it
by default in unsupported hardware will cause some
feature disabled in hardware.
This patch will read btcoex_support flag and
wlan priority gpio pin number from DT. Depends on the
btcoex_support flag value host will expose BTCOEX support
and wlan priority gpio pin number to target.

Testing:
	* Tested HW : QCA4019
	* Tested FW : 10.4-3.2.1.1-00017

Signed-off-by: Tamizh Chelvam <tamizhr@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>