iommu/vt-d: Allow devices with RMRRs to use identity domain

Since commit ea2447f7

 ("intel-iommu: Prevent devices with
RMRRs from being placed into SI Domain"), the Intel IOMMU driver
doesn't allow any devices with RMRR locked to use the identity
domain. This was added to to fix the issue where the RMRR info
for devices being placed in and out of the identity domain gets
lost. This identity maps all RMRRs when setting up the identity
domain, so that devices with RMRRs could also use it.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>