net: phy: nxp-c45-tja11xx: add MACsec statistics

Add MACsec statistics callbacks.
The statistic registers must be set to 0 if the SC/SA is
deleted to read relevant values next time when the SC/SA is used.
Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>