arm64: dts: lx2160a-rdb: Add Inphi PHY node

DPMAC5 and DPMAC6 are connected to 25G Inphi PHY

Signed-off-by: Vicentiu Galanopulo <vicentiu.galanopulo@nxp.com>
Signed-off-by: Florin Chiculita <florinlaurentiu.chiculita@nxp.com>
Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>