OMAP: common: consolidate fake USB ethernet MAC address creation
TI platforms such as OMAP5uevm, PandaBoard, use equivalent
logic to generate fake USB MAC address from device unique DIE ID.
Consolidate this to a generic location such that other TI platforms such
as BeagleBoard-XM can also use the same.
NOTE: at this point in time, I dont yet see a need for a generic dummy
ethernet MAC address creation function, but if there is a need in the
future, this can be further abstracted out.
Signed-off-by: Nishanth Menon <nm@ti.com>