MAINTAINERS: add include/dt-bindings/pinctrl to PIN CONTROL SUBSYSTEM

Maintainers of the directory Documentation/devicetree/bindings/pinctrl
are also the maintainers of the corresponding directory
include/dt-bindings/pinctrl.

Add the file entry for include/dt-bindings/pinctrl to the appropriate
section in MAINTAINERS.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220613122955.20714-1-lukas.bulwahn@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -15708,6 +15708,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git
 F:	Documentation/devicetree/bindings/pinctrl/
 F:	Documentation/driver-api/pin-control.rst
 F:	drivers/pinctrl/
+F:	include/dt-bindings/pinctrl/
 F:	include/linux/pinctrl/
 
 PIN CONTROLLER - AMD