KVM: selftests: Add missing "break" in rseq_test's param parsing

In commit 0297cdc12a ("KVM: selftests: Add option to rseq test to
override /dev/cpu_dma_latency"), a 'break' is missed before the option
'l' in the argument parsing loop, which leads to an unexpected core
dump in atoi_paranoid(). It tries to get the latency from non-existent
argument.

  host$ ./rseq_test -u
  Random seed: 0x6b8b4567
  Segmentation fault (core dumped)

Add a 'break' before the option 'l' in the argument parsing loop to avoid
the unexpected core dump.

Fixes: 0297cdc12a ("KVM: selftests: Add option to rseq test to override /dev/cpu_dma_latency")
Cc: stable@vger.kernel.org # v6.15+
Signed-off-by: Gavin Shan <gshan@redhat.com>
Link: https://patch.msgid.link/20251124050427.1924591-1-gshan@redhat.com
[sean: describe code change in shortlog]
Signed-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/rseq_test.c

@@ -215,6 +215,7 @@ int main(int argc, char *argv[])
 		switch (opt) {
 		case 'u':
 			skip_sanity_check = true;
+			break;
 		case 'l':
 			latency = atoi_paranoid(optarg);
 			break;