i40e: fix ethtool to get EEPROM data from X722 interface

Currently ethtool -e will error out with a X722 interface
as its EEPROM has a scope limit at offset 0x5B9FFF.
This patch fixes the issue by setting the EEPROM length to
the scope limit to avoid NVM read failure beyond that.

Change-ID: I0b7d4dd6c7f2a57cace438af5dffa0f44c229372
Signed-off-by: Lihong Yang <lihong.yang@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>