HII: Subnet Mask Prefix in the HFI Transport Info Descriptor is zero with IPv6

[tbzatek]

Not sure exactly where the problem is, using HII forms to set static IPv6 addresses. There might be two issues, likely related.

As a first step, fill in the values as follows:

Scroll down, press Save changes, Esc to previous menu and reopen the boot attempt again. Notice the prefix is lost and the values uppercase:

(would be also nice to update the help string on the right so that user knows how to specify ipv6 prefix)

This results in subnet_mask_prefix=0 in the NBFT table:

      {
        "index":2,
        "transport":"tcp",
        "pcidev":"0:0:4.0",
        "mac_addr":"52:54:00:72:c5:af",
        "vlan":0,
        "ip_origin":1,
        "ipaddr":"4321::bbbb:2",
        "subnet_mask_prefix":0,
        "gateway_ipaddr":"::",
        "route_metric":0,
        "primary_dns_ipaddr":"::",
        "secondary_dns_ipaddr":"::",
        "dhcp_server_ipaddr":"",
        "this_hfi_is_default_route":1,
        "dhcp_override":0
      }