ARM: dts: imx6qdl-apalis: Fix typo in ADC comment

Fix the spelling of 'conversion'.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-apalis.dtsi

@@ -310,7 +310,7 @@ stmpe811@41 {
 		st,mod-12b = <1>;
 		/* internal ADC reference */
 		st,ref-sel = <0>;
-		/* ADC converstion time: 80 clocks */
+		/* ADC conversion time: 80 clocks */
 		st,sample-time = <4>;
 
 		stmpe_touchscreen: stmpe-touchscreen {