selftests: mm: ksm: fix incorrect evaluation of parameter

A missing break in kms_tests leads to kselftest hang when the parameter -s
is used.

In current code flow because of missing break in -s, -t parses args
spilled from -s and as -t accepts only valid values as 0,1 so any arg in
-s >1 or <0, gets in ksm_test failure

This went undetected since, before the addition of option -t, the next
case -M would immediately break out of the switch statement but that is no
longer the case

Add the missing break statement.

----Before----
./ksm_tests -H -s 100
Invalid merge type

----After----
./ksm_tests -H -s 100
Number of normal pages:    0
Number of huge pages:    50
Total size:    100 MiB
Total time:    0.401732682 s
Average speed:  248.922 MiB/s

Link: https://lkml.kernel.org/r/20230728163952.4634-1-ayush.jain3@amd.com
Fixes: 07115fcc ("selftests/mm: add new selftests for KSM")
Signed-off-by: Ayush Jain <ayush.jain3@amd.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Stefan Roesch <shr@devkernel.io>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/ksm_tests.c

@@ -831,6 +831,7 @@ int main(int argc, char *argv[])
 				printf("Size must be greater than 0\n");
 				return KSFT_FAIL;
 			}
+			break;
 		case 't':
 			{
 				int tmp = atoi(optarg);