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

net: mlxsw: 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 mlxsw driver to the new API, so that the
ndo_eth_ioctl() path can be removed completely.

The UAPI is still ioctl-only, but it's best to remove the "ioctl"
mentions from the driver in case a netlink variant appears.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250512154411.848614-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>