iommu: Introduce new 'struct iommu_device'

iommu: Introduce new 'struct iommu_device'

This struct represents one hardware iommu in the iommu core
code. For now it only has the iommu-ops associated with it,
but that will be extended soon.

The register/unregister interface is also added, as well as
making use of it in the Intel and AMD IOMMU drivers.

BugLink: http://bugs.launchpad.net/bugs/1688158
Signed-off-by: Joerg Roedel <jroedel@suse.de>
(cherry picked from commit b0119e870837dcd15a207b4701542ebac5d19b45)
Signed-off-by: Manoj Iyer <manoj.iyer@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>