ice: refactor unwind cleanup in eswitch mode

The code for supporting eswitch mode and port representors on VFs uses
an unwind based cleanup flow when handling errors.

These flows are used to cleanup and get everything back to the state
prior to attempting to switch from legacy to representor mode or back.

The unwind iterations make sense, but complicate a plan to refactor the
VF array structure. In the future we won't have a clean method of
reversing an iteration of the VFs.

Instead, we can change the cleanup flow to just iterate over all VF
structures and clean up appropriately.

First notice that ice_repr_add_for_all_vfs and ice_repr_rem_from_all_vfs
have an additional step of re-assigning the VC ops. There is no good
reason to do this outside of ice_repr_add and ice_repr_rem. It can
simply be done as the last step of these functions.

Second, make sure ice_repr_rem is safe to call on a VF which does not
have a representor. Check if vf->repr is NULL first and exit early if
so.

Move ice_repr_rem_from_all_vfs above ice_repr_add_for_all_vfs so that we
can call it from the cleanup function.

In ice_eswitch.c, replace the unwind iteration with a call to
ice_eswitch_release_reprs. This will go through all of the VFs and
revert the VF back to the standard model without the eswitch mode.

To make this safe, ensure this function checks whether or not the
represent or has been moved. Rely on the metadata destination in
vf->repr->dst. This must be NULL if the representor has not been moved
to eswitch mode.

Ensure that we always re-assign this value back to NULL after freeing
it, and move the ice_eswitch_release_reprs so that it can be called from
the setup function.

With these changes, eswitch cleanup no longer uses an unwind flow that
is problematic for the planned VF data structure change.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>