MIPS: Octeon: fix CN6640 hang on XAUI init

Some CN66XX series Octeon II chips seem to hang if a reset is issued on
XAUI initialization. Avoid the hang by disabling the reset.

Tested on SNIC10E.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>