tools/testing/selftests/vm/hmm-tests.c: use the new SKIP() macro

Some tests might not be able to be run if resources like huge pages are
not available.  Mark these tests as skipped instead of simply passing.

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Shuah Khan <shuah@kernel.org>
Link: http://lkml.kernel.org/r/20200827190400.12608-1-rcampbell@nvidia.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>