net: phy: nxp-c45-tja11xx: add remove callback

Unregister PTP clock when the driver is removed.
Purge the RX and TX skb queues.

Fixes: 514def5d

 ("phy: nxp-c45-tja11xx: add timestamping support")
CC: stable@vger.kernel.org # 5.15+
Signed-off-by: Radu Pirea (OSS) <radu-nicolae.pirea@oss.nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20230406095904.75456-1-radu-nicolae.pirea@oss.nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>