net: dsa: sja1105: Actually implement the P/Q/R/S FDB bits

In commit 1da73821 ("net: dsa: sja1105: Add FDB operations for
P/Q/R/S series"), these bits were set in the static config, but
apparently they did not do anything.  The reason is that the packing
accessors for them were part of a patch I forgot to send.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>