i40e: add priv flag for automatic rule eviction

The X722 can support automatic rule eviction for automatically added
flow director rules.  Feature is (should be) disabled by default.

Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>