iommupt: Optimize the gather processing for DMA-FQ mode

iommupt: Optimize the gather processing for DMA-FQ mode

In PT_FEAT_FLUSH_RANGE mode the gather was accumulated but never flushed
and then the accumulated range was discarded by the dma-iommu code in
DMA-FQ mode. This is basically optimal.

However for PT_FEAT_FLUSH_RANGE_NO_GAPS the page table would push flushes
that are redundant with the flush all generated by the DMA-FQ mode.

Disable all range accumulation in the gather, and iommu_pt triggered
flushing when in iommu_iotlb_gather_queued() indicates it is in DMA-FQ
mode.

Reported-by: Robin Murphy <robin.murphy@arm.com>
Closes: https://lore.kernel.org/r/794b6121-b66b-4819-b291-9761ed21cd83@arm.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>