MAINTAINERS: add DT binding docs for AT24

The driver gained DT support recently, so we should add the binding docs
in the MAINTAINERS file.
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

MAINTAINERS

@@ -2263,6 +2263,7 @@ AT24 EEPROM DRIVER
 M:	Bartosz Golaszewski <brgl@bgdev.pl>
 L:	linux-i2c@vger.kernel.org
 S:	Maintained
+F:	Documentation/devicetree/bindings/eeprom/at24.txt
 F:	drivers/misc/eeprom/at24.c
 F:	include/linux/platform_data/at24.h