ARM: dts: vf: Add memory node unit name

Include memory node unit name in order to fix the following W=1
warnings:

Warning (unit_address_vs_reg): Node /memory has a reg or ranges property, but no unit name

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>