ARM: dts: vesnin: Add unit address for memory node

Fixes the following warnings:

arch/arm/boot/dts/aspeed-bmc-opp-vesnin.dt.yaml: /: memory: False schema does not allow {'reg': [[1073741824, 536870912]]}
arch/arm/boot/dts/aspeed-bmc-opp-vesnin.dt.yaml: memory: 'device_type' is a required property

Cc: Alexander Filippov <[e-mail]>
Signed-off-by: Andrew Jeffery <[e-mail]>
Reviewed-by: Joel Stanley <[e-mail]>
Tested-by: Alexander Filippov <[e-mail]>
Signed-off-by: Joel Stanley <[e-mail]>

arch/arm/boot/dts/aspeed-bmc-opp-vesnin.dts

···
 		bootargs = "console=ttyS4,115200 earlyprintk";
 	};
 
-	memory {
+	memory@40000000 {
 		reg = <0x40000000 0x20000000>;
 	};