MAINTAINERS: add info for e3x0-button driver

Signed-off-by: NMoritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

MAINTAINERS

@@ -3277,6 +3277,14 @@ M:	"Maciej W. Rozycki" <macro@linux-mips.org>
 S:	Maintained
 F:	drivers/tty/serial/dz.*
 
+E3X0 POWER BUTTON DRIVER
+M:	Moritz Fischer <moritz.fischer@ettus.com>
+L:	usrp-users@lists.ettus.com
+W:	http://www.ettus.com
+S:	Supported
+F:	drivers/input/misc/e3x0-button.c
+F:	Documentation/devicetree/bindings/input/e3x0-button.txt
+
 E4000 MEDIA DRIVER
 M:	Antti Palosaari <crope@iki.fi>
 L:	linux-media@vger.kernel.org