net: phy: mscc: PN rollover support

This patch adds support for handling MACsec PN rollover in the mscc PHY
driver. When a flow rolls over, an interrupt is fired. This patch adds
the logic to check all flows and identify the one rolling over in the
handle_interrupt PHY helper, then disables the flow and report the event
to the MACsec core.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>