net: marvell: prestera: uninitialized variable bug

The "ret" variable needs to be initialized at the start.

Fixes: 52323ef7

 ("net: marvell: prestera: add phylink support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YuKeBBuGtsmd7QdT@kili
Signed-off-by: Jakub Kicinski <kuba@kernel.org>