iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

In removing IOMMU_CAP_DEFERRED_FLUSH, the below referenced commit
was over-eager in removing the return, resulting in the test for
IOMMU_CAP_CACHE_COHERENCY falling through to an irrelevant option.

Restore dropped return.

Fixes: 1c18a1212c77 ("iommu/dma: Always allow DMA-FQ when iommupt provides the iommu_domain")
Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Will Deacon <will@kernel.org>