ice: move ice_vf_vsi_release into ice_vf_lib.c

The ice_vf_vsi_release function will be used in a future change to
refactor the .vsi_rebuild function. Move this over to ice_vf_lib.c so
that it can be used there.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Marek Szlosek <marek.szlosek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>