MAINTAINERS: Add the DT binding to the ath9k file list

Changes to the DT binding should also be sent to the ath9k list.

Signed-off-by: Alban Bedel <albeu@free.fr>
---
Changelog:
v2: * Fixed From/SoB to have my full name

MAINTAINERS

@@ -11496,6 +11496,7 @@ L:	linux-wireless@vger.kernel.org
 W:	http://wireless.kernel.org/en/users/Drivers/ath9k
 S:	Supported
 F:	drivers/net/wireless/ath/ath9k/
+F:	Documentation/devicetree/bindings/net/wireless/qca,ath9k.txt
 
 QUALCOMM CAMERA SUBSYSTEM DRIVER
 M:	Todor Tomov <todor.tomov@linaro.org>