ice: Introduce a local variable for a VSI in the rebuild path

When a VSI is accessed inside the ice_for_each_vsi macro in the rebuild
path (ice_vsi_rebuild_all() and ice_vsi_replay_all()), it is referred to
as pf->vsi[i]. Introduce local variables to improve readability.

Signed-off-by: Krzysztof Kazimierczak <krzysztof.kazimierczak@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>