vfio: selftests: add end of address space DMA map/unmap tests

Add tests which validate dma map/unmap at the end of address space. Add
negative test cases for checking that overflowing ioctl args fail with
the expected errno.

Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Alex Mastro <amastro@fb.com>
Link: https://lore.kernel.org/r/20251028-fix-unmap-v6-5-2542b96bcc8e@fb.com


Signed-off-by: Alex Williamson <alex@shazbot.org>