vfio: selftests: Add driver for Intel DSA

vfio: selftests: Add driver for Intel DSA

Add a driver to VFIO selftests for Intel DSA devices.

For now the driver only supports up to 32 batches and 1024 copies per
batch, which were the limits of the hardware this commit was tested
with. This is sufficient to generate 9+ minutes of DMA memcpys at a rate
of over 30 GB/s. This should be plenty to stress test VFIO and the IOMMU.

The driver does not yet support requesting interrupt handles, as this
commit was not tested against hardware that requires it.

Cc: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20250822212518.4156428-23-dmatlack@google.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>