iommufd: Allow MMIO pages in a batch

iommufd: Allow MMIO pages in a batch

Addresses intended for MMIO should be propagated through to the iommu with
the IOMMU_MMIO flag set.

Keep track in the batch if all the pfns are cachable or mmio and flush the
batch out of it ever needs to be changed. Switch to IOMMU_MMIO if the
batch is MMIO when mapping the iommu.

Link: https://patch.msgid.link/r/5-v2-b2c110338e3f+5c2-iommufd_dmabuf_jgg@nvidia.com
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Shuai Xue <xueshuai@linux.alibaba.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>