net: phy: add genphy_c45_pma_suspend/resume

Add generic PMA suspend and resume callback functions for C45 PHYs.

Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>