What register settings are needed to set the MAX3420/21 to produce the HS USB test pattern so that we can capture an eye diagram?

The MAX3420 operates as a USB full speed (12 Mbps) device.  The standard USB test pattern mentioned in the question is specific to USB high speed (480 Mbps) devices, so it is not possible to simply set an internal register and force the generation of the USB test pattern. Please see the USB.org web site and review the full speed signal quality test procedure for detailed steps appropriate to the MAX3420.