It turns out that the disable_dmar_iommu() code-path tried
to get the device_domain_lock recursivly, which will
dead-lock when this code runs on dmar removal. Fix both
code-paths that could lead to the dead-lock.

Fixes: 55d94043 ('iommu/vt-d: Get rid of domain->iommu_lock')
Signed-off-by: Joerg Roedel <jroedel@suse.de>