net: dsa: sja1105: unconditionally set DESTMETA and SRCMETA in AVB table

These fields configure the destination and source MAC address that the
switch will put in the Ethernet frames sent towards the CPU port that
contain RX timestamps for PTP.

These fields do not enable the feature itself, that is configured via
SEND_META0 and SEND_META1 in the General Params table.

The implication of this patch is that the AVB Params table will always
be present in the static config. Which doesn't really hurt.

This is needed because in a future patch, we will add another field from
this table, CAS_MASTER, for configuring the PTP_CLK pin function. That
can be configured irrespective of whether RX timestamping is enabled or
not, so always having this table present is going to simplify things a
bit.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>