mips: octeon: Add cvmx-xcv-defs.h header file

Import cvmx-xcv-defs.h header file from 2013 U-Boot. It will be used
by the later added drivers to support networking on the MIPS Octeon II /
III platforms.

Signed-off-by: Aaron Williams <awilliams@marvell.com>
Signed-off-by: Stefan Roese <sr@denx.de>