net: mvpp2: convert to ndo_hwtstamp_get() and ndo_hwtstamp_set()

net: mvpp2: convert to ndo_hwtstamp_get() and ndo_hwtstamp_set()

New timestamping API was introduced in commit 66f7223039c0 ("net: add
NDOs for configuring hardware timestamping") from kernel v6.6. It is
time to convert the mvpp2 driver to the new API, so that the
ndo_eth_ioctl() path can be removed completely.

Note that on the !port->hwtstamp condition, the old code used to fall
through in mvpp2_ioctl(), and return either -ENOTSUPP if !port->phylink,
or -EOPNOTSUPP, in phylink_mii_ioctl(). Keep the test for port->hwtstamp
in the newly introduced net_device_ops, but consolidate the error code
to just -EOPNOTSUPP. The other one is documented as NFS-specific, it's
best to avoid it anyway.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250508144630.1979215-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>