iommu: Make iommu_device_link/unlink take a struct iommu_device

iommu: Make iommu_device_link/unlink take a struct iommu_device

This makes the interface more consistent with
iommu_device_sysfs_add/remove.

BugLink: http://bugs.launchpad.net/bugs/1688158
Signed-off-by: Joerg Roedel <jroedel@suse.de>
(cherry picked from commit e3d10af1128b6bc394f21656ff13753130f3c107)
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>