iommu/vt-d: Get rid of domain->iommu_lock

When this lock is held the device_domain_lock is also
required to make sure the device_domain_info does not vanish
while in use. So this lock can be removed as it gives no
additional protection.

Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --cc drivers/iommu/intel-iommu.c
Simple merge