memblock tests: update reference to obsolete build option in comments

The VERBOSE build option was replaced with the --verbose runtime option,
but the comments describing the ASSERT_*() macros still refer to the
VERBOSE build option. Update these comments so that they refer to the
--verbose runtime option.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Rebecca Mckeever <remckee0@gmail.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/5f8a4c2bde34cc029282c68d47eda982d950f421.1660451025.git.remckee0@gmail.com