phy: nxp-c45-tja11xx: add timestamping support

Add mii_timestamper interface and register a ptp clock.
The package timestamping can work with or without interrupts.
RX timestamps are received in the reserved field of the PTP package.
TX timestamps are read via MDIO from a set of registers.
Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>