net: dpaa2-eth: add ndo_hwtstamp_get() implementation

net: dpaa2-eth: add ndo_hwtstamp_get() implementation

Allow SIOCGHWTSTAMP to retrieve the current timestamping settings on
DPNIs. This reflects what has been done in dpaa2_eth_hwtstamp_set().

Tested with hwstamp_ctl -i endpmac17. Before the change, it prints
"Device driver does not have support for non-destructive SIOCGHWTSTAMP."
After the change, it retrieves the previously set configuration.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com> # LX2160A
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250508134102.1747075-2-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>