At the very end of the MACsec block initialization in the MSCC PHY
driver, the MACsec "protocol mode" is set. This setting should be set
based on the PHY id within the package, as the bank used to access the
register used depends on this. This was not done correctly, and only the
first bank was used leading to the two upper PHYs being unstable when
using the VSC8584. This patch fixes it.

Fixes: 1bbe0ecc ("net: phy: mscc: macsec initialization")
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>