net: pch_gbe: convert to use ndo_hwtstamp callbacks

net: pch_gbe: convert to use ndo_hwtstamp callbacks

The driver implemented SIOCSHWTSTAMP ioctl command only, but it stores
configuration in the private data, so it is possible to report it back
to users. Implement both ndo_hwtstamp_set and ndo_hwtstamp_get
callbacks. To properly report RX filter type, store it in hwts_rx_en
instead of using this field as a simple flag. The logic didn't change
because receive path used this field as boolean flag.

Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20251103150952.3538205-7-vadim.fedorenko@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>