eeprom: at24: fix reading from 24MAC402/24MAC602

Chip datasheet mentions that word addresses other than the actual
start position of the MAC delivers undefined results. So fix this.
Current implementation doesn't work due to this wrong offset.

Cc: stable@vger.kernel.org
Fixes: 0b813658

 ("eeprom: at24: add support for at24mac series")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>