ethtool: Add SFF-8436 and SFF-8636 max EEPROM length definitions

Added max EEPROM length defines for ethtool usage:
 #define ETH_MODULE_SFF_8636_MAX_LEN     640
 #define ETH_MODULE_SFF_8436_MAX_LEN     640

These definitions are used to determine the EEPROM
data length when reading high eeprom pages.

For example, SFF-8636 EEPROM data from page 03h
needs to be stored at data[512] - data[639].

Signed-off-by: Erez Alfasi <ereza@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>