phylink: Fix an uninitialized variable bug

"ret" isn't necessarily initialized here.

Fixes: 9525ae83

 ("phylink: add phylink infrastructure")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>