snmp_pf: fix pfInterfacesIfRefsState

[kp]

Summary

pfInterfacesIfRefsState was described as 'Null', which upset bsnmpwalk's attempt
to resolve OIDs to symbolic names:

bsnmpwalk: Error adding leaf pfInterfacesIfRefsState to list

This was done back in d6d3f01e0a339, because we don't return this value any
more. Return it to 'Unsigned32', which fixes things, even if we still don't
actually return this value.

Event: Tokyo Hackathon 202503

[philip]

This looks good to me. Go ahead and commit this.

While you're there, please update the metadata:

ORGANIZATION "Alternative Enterprises (HK) Limited"

And remove the Postal: address.

[philip]

...and remember to update the date stamps and type something in a REVISION... :)

[kp]

Update ORGANIZATION and LAST-UPDATED

[philip]

Thanks. LGTM.