KVM: selftests: Use X86_PROPERTY_MAX_KVM_LEAF in CPUID test

Use X86_PROPERTY_MAX_KVM_LEAF to replace the equivalent open coded check
on KVM's maximum paravirt CPUID leaf.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221006005125.680782-5-seanjc@google.com

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

@@ -43,15 +43,6 @@ static void test_guest_cpuids(struct kvm_cpuid2 *guest_cpuid)
 
 }
 
-static void test_cpuid_40000000(struct kvm_cpuid2 *guest_cpuid)
-{
-	u32 eax, ebx, ecx, edx;
-
-	cpuid(0x40000000, &eax, &ebx, &ecx, &edx);
-
-	GUEST_ASSERT(eax == 0x40000001);
-}
-
 static void guest_main(struct kvm_cpuid2 *guest_cpuid)
 {
 	GUEST_SYNC(1);
@@ -60,7 +51,7 @@ static void guest_main(struct kvm_cpuid2 *guest_cpuid)
 
 	GUEST_SYNC(2);
 
-	test_cpuid_40000000(guest_cpuid);
+	GUEST_ASSERT(this_cpu_property(X86_PROPERTY_MAX_KVM_LEAF) == 0x40000001);
 
 	GUEST_DONE();
 }