ice: Refactor PR ethtool ops

This patch improves a few things:

- it fixes issue where ethtool -i reports that PR supports
  priv-flags and tests when in fact it does not support them
- instead of using the same functions for both PF and PR ethtool ops,
  this patch introduces separate ops for both cases and internal
  functions with core logic.
- prevent accessing VF VSI while VF is not ready by calling
  ice_check_vf_ready_for_cfg
- all PR specific functions in ethtool.c were moved to one place in
  file
- instead overwriting n_priv_flags in ice_repr_get_drvinfo,
  priv-flags code was moved from __ice_get_drvinfo to ice_get_drvinfo

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>