net: mvpp2: add support for hardware timestamps

net: mvpp2: add support for hardware timestamps

Add support for hardware timestamps in (e.g.) the PHY by calling
skb_tx_timestamp() as close as reasonably possible to the point that
the hardware is instructed to send the queued packets.

As this also introduces software timestamping support, report those
capabilities via the .get_ts_info() method.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1uy82E-00000005Sll-0SSy@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>