KVM: x86: hide KVM_HC_CLOCK_PAIRING on 32 bit

The newly added hypercall doesn't work on x86-32:

arch/x86/kvm/x86.c: In function 'kvm_pv_clock_pairing':
arch/x86/kvm/x86.c:6163:6: error: implicit declaration of function 'kvm_get_walltime_and_clockread';did you mean 'kvm_get_time_scale'? [-Werror=implicit-function-declaration]

This adds an #ifdef around it, matching the one around the related
functions that are also only implemented on 64-bit systems.

Fixes: 55dd00a73a51 ("KVM: x86: add KVM_HC_CLOCK_PAIRING hypercall")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -6148,6 +6148,7 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_halt);
 
+#ifdef CONFIG_X86_64
 static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
 			        unsigned long clock_type)
 {
@@ -6174,6 +6175,7 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
 
 	return ret;
 }
+#endif
 
 /*
  * kvm_pv_kick_cpu_op:  Kick a vcpu.
@@ -6239,9 +6241,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 		kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
 		ret = 0;
 		break;
+#ifdef CONFIG_X86_64
 	case KVM_HC_CLOCK_PAIRING:
 		ret = kvm_pv_clock_pairing(vcpu, a0, a1);
 		break;
+#endif
 	default:
 		ret = -KVM_ENOSYS;
 		break;