win32-aio: Fix how win32_aio_process_completion() frees buffer win32_aio_submit() allocates it with qemu_blockalign(), therefore it must be freed with qemu_vfree(), not g_free(). Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>