Staging: Add octeon-ethernet driver files.

The octeon-ethernet driver supports the sgmii, rgmii, spi, and xaui
ports present on the Cavium OCTEON family of SOCs.  These SOCs are
multi-core mips64 processors with existing support over in arch/mips.

The driver files can be categorized into three basic groups:

1) Register definitions, these are named cvmx-*-defs.h

2) Main driver code, these have names that don't start cvmx-.

3) Interface specific functions and other utility code, names starting
with cvmx-

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>