nfp: add support for eeprom get and set command

Add support for eeprom get and set operation with ethtool command.
with this change, we can support commands as:

 #ethtool -e enp101s0np0 offset 0 length 6
 Offset          Values
 ------          ------
 0x0000:         00 15 4d 16 66 33

 #ethtool -E enp101s0np0 magic 0x400019ee offset 5 length 1 value 0x88

We make this change to persist MAC change during driver reload and system
reboot.

Signed-off-by: Baowen Zheng <baowen.zheng@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>