iommu: Use right function to get group for device

iommu: Use right function to get group for device

[ Upstream commit 57274ea25736496ee019a5c40479855b21888839 ]

The iommu_group_get_for_dev() will allocate a group for a
device if it isn't in any group. This isn't the use case
in iommu_request_dm_for_dev(). Let's use iommu_group_get()
instead.

Fixes: d290f1e70d85a ("iommu: Introduce iommu_request_dm_for_dev()")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>