net: mscc: ocelot: don't report that RX timestamping is enabled by default

net: mscc: ocelot: don't report that RX timestamping is enabled by default

PTP RX timestamping should be enabled when the user requests it, not by
default. If it is enabled by default, it can be problematic when the
ocelot driver is a DSA master, and it sidesteps what DSA tries to avoid
through __dsa_master_hwtstamp_validate().

Additionally, after the change which made ocelot trap PTP packets only
to the CPU at ocelot_hwtstamp_set() time, it is no longer even true that
RX timestamping is enabled by default, because until ocelot_hwtstamp_set()
is called, the PTP traps are actually not set up. So the rx_filter field
of ocelot->hwtstamp_config reflects an incorrect reality.

Fixes: 96ca08c05838 ("net: mscc: ocelot: set up traps for PTP packets")
Fixes: 4e3b0468e6d7 ("net: mscc: PTP Hardware Clock (PHC) support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>