This changes the pfilter rule-set, to make it ready for vlan addition.
Moreover, it removes the choice between three rule-sets and uses one
that works for everyone (we'll add the vlan option later on).

Moreover, we prepare for the option of peer-delay PTP and UDP-based PTP.

As a side effect, one Kconfig option is removed.

We know for sure that what goes to the "streamer" protocol
is re-checked, so the streamer can get some "everything else", exactly
like the 7S wr-nic (that sends to the host everything unused).

This is the current rule set:

     - everything tagged is dropped
     - CPU: arp broadcast, not unicast (i.e. requests only).
     - CPU: PTP ethtype. Any mac address.
     - CPU: ICMP unicast, not broadcast.
     - CPU: UDP (uni/multicast), ports  bootpc, ptp-event, ptp-general.
     - Etherbone (class 7): UDP (uni/multicast) and port 0xebd0
     - Other fabric (class 6): anything not Etherbone (inverted class 7 bit)

This counts up to 28 rules. We have 4 more rules available and we may
add options, either at build time or run time to add udp ports or
other ethertypes.  Or not...

2 caveats:

  - frames for the CPU will have class bits 0x41 instead of 0x01, because
  everything not etherbone will receive bit 6. This is not a problem, as
  the CPU is not checking the class bits.

  - the wr-nic gateware, when using this new sw code base, must be
  changed to use classes 6 and 7 like everybody else, not classes 7
  and 5.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>