vfio: fix DMA mapping granularity for IOVA as VA

vfio: fix DMA mapping granularity for IOVA as VA

Partial unmapping is not supported for VFIO IOMMU type1
by kernel. Though kernel gives return as zero, the unmapped size
returned will not be same as expected. So check for
returned unmap size and return error.

For IOVA as PA, DMA mapping is already at memseg size
granularity. Do the same even for IOVA as VA mode as
DMA map/unmap triggered by heap allocations,
maintain granularity of memseg page size so that heap
expansion and contraction does not have this issue.

For user requested DMA map/unmap disallow partial unmapping
for VFIO type1.

Fixes: 73a639085938 ("vfio: allow to map other memory regions")
Cc: stable@dpdk.org
Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: David Christensen <drc@linux.vnet.ibm.com>