arm64: dts: lx2160a: add emdio2 node

Add a description for the emdio2 controller to the lx2160a dtsi file,
so we can use it in the SolidRun Clearfog CX platform.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>