Use OCP's IANA Enterprise number for the VIVSO DHPC Request

The DHCP Vendor-Identifying Vendor-Specific Information (VIVSO) option
requires an IANA enterprise number to identify a unique VIVSO
namespace.  See RFC-3925.

When the ONIE project started the Open Compute Project did not have an
IANA number.  Now it does.  Start using their number now.