ARM: dts: imx6ul: mba6ulx: Fix stmpe811 node warnings

interrupt-controller is only valid for gpio subnode, remove it.
Rename touchscreen subnode according to bindings.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Author: tq-steina

arch/arm/boot/dts/nxp/imx/mba6ulx.dtsi

@@ -277,10 +277,9 @@
 		reg = <0x41>;
 		interrupts = <21 IRQ_TYPE_EDGE_FALLING>;
 		interrupt-parent = <&gpio4>;
-		interrupt-controller;
 		status = "disabled";
 
-		stmpe_touchscreen {
+		touchscreen {
 			compatible = "st,stmpe-ts";
 			st,adc-freq = <1>;      /* 3.25 MHz ADC clock speed */
 			st,ave-ctrl = <3>;      /* 8 sample average control */