KVM: selftests: Fix inverted "warning" in access tracking perf test

Warn if the number of idle pages is greater than or equal to 10% of the
total number of pages, not if the percentage of idle pages is less than
10%. The original code asserted that less than 10% of pages were still
idle, but the check got inverted when the assert was converted to a
warning.

Opportunistically clean up the warning; selftests are 64-bit only, there
is no need to use "%PRIu64" instead of "%lu".

Fixes: 6336a810db5c ("KVM: selftests: replace assertion with warning in access_tracking_perf_test")
Reviewed-by: Emanuele Giuseppe Esposito <[e-mail]>
Signed-off-by: Sean Christopherson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

tools/testing/selftests/kvm/access_tracking_perf_test.c

···
 	 * happens, much more pages are cached there and guest won't see the
 	 * "idle" bit cleared.
 	 */
-	if (still_idle < pages / 10)
-		printf("WARNING: vCPU%d: Too many pages still idle (%" PRIu64
-		       "out of %" PRIu64 "), this will affect performance results"
-		       ".\n",
+	if (still_idle >= pages / 10)
+		printf("WARNING: vCPU%d: Too many pages still idle (%lu out of %lu), "
+		       "this will affect performance results.\n",
 		       vcpu_idx, still_idle, pages);
 
 	close(page_idle_fd);