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 <a.filippov@yadro.com>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Tested-by: Alexander Filippov <a.filippov@yadro.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>