ice: Free VSI contexts during for unload

In the unload path, all VSIs are freed. Also free the related VSI
contexts to prevent memory leaks.

Signed-off-by: Victor Raj <victor.raj@intel.com>
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>