MAINTAINERS: Update OMAP GPIO driver entry

I'm not as involved in OMAP as I used to be and Grygorii is the most
active developer working on this driver and has also been reviewing
patches so let's add him as a driver maintainer instead of me.

While being there, add the driver's DT binding doc to the file list.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -7788,11 +7788,12 @@ F:	drivers/usb/*/*omap*
 F:	arch/arm/*omap*/usb*
 
 OMAP GPIO DRIVER
-M:	Javier Martinez Canillas <javier@dowhile0.org>
+M:	Grygorii Strashko <grygorii.strashko@ti.com>
 M:	Santosh Shilimkar <ssantosh@kernel.org>
 M:	Kevin Hilman <khilman@deeprootsystems.com>
 L:	linux-omap@vger.kernel.org
 S:	Maintained
+F:	Documentation/devicetree/bindings/gpio/gpio-omap.txt
 F:	drivers/gpio/gpio-omap.c
 
 OMAP/NEWFLOW NANOBONE MACHINE SUPPORT