mips: octeon: Add cvmx-pki.c

Import cvmx-pki.c 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>