ARM: dts: Drop serial 1 alias on GW7001

The Gateaway 7001 has a serial port alias for serial1, this has
proven detrimental on the WG302 so remove it on this machine
as well.

Drop in a small comment that this machine is based on IXP422.

Cc: Zoltan HERPAI <wigyori@uid0.hu>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/intel-ixp42x-gateway-7001.dts

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: ISC
 /*
- * Device Tree file for Gateway 7001 AP
+ * Device Tree file for Gateway 7001 AP based on IXP422
  * Derived from boardfiles written by Imre Kaloz
  */
 
@@ -29,7 +29,6 @@
 	aliases {
 		/* second UART is the primary console */
 		serial0 = &uart1;
-		serial1 = &uart0;
 	};
 
 	soc {