selftests/mm: deduplicate test names in madv_populate

The madv_populate selftest has some repetitive code for several different
cases that it covers, included repeated test names used in
ksft_test_result() reports.  This causes problems for automation, the test
name is used to both track the test between runs and distinguish between
multiple tests within the same run.  Fix this by tweaking the messages
with duplication to be more specific about the contexts they're in.

Link: https://lkml.kernel.org/r/20250522-selftests-mm-madv-populate-dedupe-v1-1-fd1dedd79b4b@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>