boards: posix: native_posix: Rename input-sdl-touch node

Rename the input-sdl-touch node to be able to have phandle references to
it.

Signed-off-by: Fabian Blatz <[email protected]>

Author: faxe1008

boards/posix/native_posix/native_posix.dts

@@ -179,7 +179,7 @@
 		width = <320>;
 	};
 
-	input-sdl-touch {
+	input_sdl_touch: input-sdl-touch {
 		compatible = "zephyr,input-sdl-touch";
 		kscan_input: kscan-input {
 			compatible = "zephyr,kscan-input";