net: stmmac: mdio: fix incorrect phy address check

net: stmmac: mdio: fix incorrect phy address check

max_addr is the max number of addresses, not the highest possible address,
therefore check phydev->mdio.addr > max_addr isn't correct.
To fix this change the semantics of max_addr, so that it represents
the highest possible address. IMO this is also a little bit more intuitive
wrt name max_addr.

Fixes: 4a107a0e8361 ("net: stmmac: mdio: use phy_find_first to simplify stmmac_mdio_register")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Reported-by: Simon Horman <horms@kernel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/e869999b-2d4b-4dc1-9890-c2d3d1e8d0f8@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>