lib/test_vmalloc.c: minor fixes to test_vmalloc.c

lib/test_vmalloc.c: minor fixes to test_vmalloc.c

If PAGE_SIZE is larger than 4k and if you have a system with a large
number of CPUs, this test can require a very large amount of memory
leading to oom-killer firing.  Given the type of allocation, the kernel
won't have anything to kill, causing the system to stall.

Add a parameter to the test_vmalloc driver to represent the number of
times a percpu object will be allocated.  Calculate this in
test_vmalloc.sh to be 90% of available memory or the current default of
35000, whichever is smaller.

Link: https://lkml.kernel.org/r/20251201181848.1216197-1-audra@redhat.com
Signed-off-by: Audra Mitchell <audra@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>