KVM: selftests: Fix MWAIT error message when guest assertion fails

Print out the test and vector as intended when a guest assert fails an
assertion regarding MONITOR/MWAIT faulting.  Unfortunately, the guest
printf support doesn't detect such issues at compile-time, so the bug
manifests as a confusing error message, e.g. in the most confusing case,
the test complains that it got vector "0" instead of expected vector "0".

Fixes: 0f52e4a ("KVM: selftests: Convert the MONITOR/MWAIT test to use printf guest asserts")
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20231107182159.404770-1-seanjc@google.com
Link: https://lore.kernel.org/r/20231129224916.532431-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c

@@ -27,10 +27,12 @@ do {									\
 									\
 	if (fault_wanted)						\
 		__GUEST_ASSERT((vector) == UD_VECTOR,			\
-			       "Expected #UD on " insn " for testcase '0x%x', got '0x%x'", vector); \
+			       "Expected #UD on " insn " for testcase '0x%x', got '0x%x'", \
+			       testcase, vector);			\
 	else								\
 		__GUEST_ASSERT(!(vector),				\
-			       "Expected success on " insn " for testcase '0x%x', got '0x%x'", vector); \
+			       "Expected success on " insn " for testcase '0x%x', got '0x%x'", \
+			       testcase, vector);			\
 } while (0)
 
 static void guest_monitor_wait(int testcase)