net: phylink: handle NA interface mode in phylink_fwnode_phy_connect()

Commit 4904b6ea ("net: phy: phylink: Use PHY device interface if
N/A") introduced handling for the phy interface mode where this is not
known at phylink creation time. This was never added to the OF/fwnode
paths, but is necessary when the phy is present in DT, but the phy-mode
is not specified.

Add this handling.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>