Input: e3x0-button - update Kconfig description

The driver is now used for the entire USRP e3xx series,
this commit fixes the description that will be displayed in
the menu accordingly.
Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/Kconfig

@@ -94,11 +94,11 @@ config INPUT_BMA150
 	  module will be called bma150.
 
 config INPUT_E3X0_BUTTON
-	tristate "NI Ettus Research USRP E3x0 Button support."
+	tristate "NI Ettus Research USRP E3xx Button support."
 	default n
 	help
 	  Say Y here to enable support for the NI Ettus Research
-	  USRP E3x0 Button.
+	  USRP E3xx Button.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called e3x0_button.