iommu/vt-d: Move deferred device attachment into helper function

iommu/vt-d: Move deferred device attachment into helper function

commit 034d98cc0cdcde2415c6f598fa9125e3eaa02569 upstream.

Move the code that does the deferred device attachment into a separate
helper function.

Fixes: 1ee0186b9a12 ("iommu/vt-d: Refactor find_domain() helper")
Cc: stable@vger.kernel.org # v5.5
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>