Update the functions which free msix_entries and q_vectors so that they
are safe against NULL values. This allows calling code to not care
whether these have already been freed when disabling and freeing them.

Change-ID: I31bfd1c0da18023d971b618edc6fb049721f3298
Signed-off-by: NJacob Keller <jacob.e.keller@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>