ice: Cleanup ice_vsi_alloc_q_vectors

1. Remove local variable num_q_vectors and use vsi->num_q_vectors instead
2. Remove local variable pf and pass vsi->back to ice_pf_to_dev

Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>