net/mlx4_en: ethtool, Remove unsupported SFP EEPROM high pages query

Querying EEPROM high pages data for SFP module is currently
not supported by our driver but is still tried, resulting in
invalid FW queries.

Set the EEPROM ethtool data length to 256 for SFP module to
limit the reading for page 0 only and prevent invalid FW queries.

Fixes: 7202da8b ("ethtool, net/mlx4_en: Cable info, get_module_info/eeprom ethtool support")
Signed-off-by: Erez Alfasi <ereza@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>