can: peak_canfd: advertise timestamping capabilities and add ioctl support

Currently, userland has no method to query which timestamping features
are supported by the peak_canfd driver (aside maybe of getting RX
messages and observe whether or not hardware timestamps stay at zero).

The canonical way to add hardware timestamp support is to implement
ethtool_ops::get_ts_info() in order to advertise the timestamping
capabilities and to implement net_device_ops::ndo_eth_ioctl() as
requested in [1]. Currently, the driver only supports hardware RX
timestamps [2] but not hardware TX. For this reason, the generic
function can_ethtool_op_get_ts_info_hwts() and can_eth_ioctl_hwts()
can not be reused and instead this patch adds peak_get_ts_info() and
peak_eth_ioctl().

[1] kernel doc Timestamping, section 3.1: "Hardware Timestamping
Implementation: Device Drivers"
Link: https://docs.kernel.org/networking/timestamping.html#hardware-timestamping-implementation-device-drivers

[2] https://lore.kernel.org/linux-can/20220727084257.brcbbf7lksoeekbr@pengutronix.de/

CC: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/20220727101641.198847-14-mailhol.vincent@wanadoo.fr
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>