Fixes Coverity issue:
CID 1436126:  Memory - illegal accesses  (USE_AFTER_FREE)

Fixes: a9e271ec ("vfio: Add migration region initialization and finalize function")
Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: David Edmondson <dme@dme.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>