igb: Garbled output for "ethtool -m"

Garbled output for "ethtool -m ethX", in igb-driven NICs with module /
plugin EEPROM (i.e. SFP information). Each output data byte appears
duplicated.

In igb_ethtool.c, igb_get_module_eeprom() is reading the EEPROM via i2c;
the eeprom offset for each word that's read via igb_read_phy_reg_i2c()
was passed in #words, whereas it needs to be a byte offset.
This patches fixes the bug.

Signed-off-by: Doron Shikmoni <doron.shikmoni@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>