vfio/pci: Fix failure to close file descriptor on error

A new error path fails to close the device file descriptor when
triggered by a ballooning incompatibility within the group.  Fix it.

Fixes: 238e9172 ("vfio/ccw/pci: Allow devices to opt-in for ballooning")
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>