KVM: MMU: audit: unregister audit tracepoints before module unloaded

fix:

Call Trace:
 [<ffffffffa01e46ba>] ? kvm_mmu_pte_write+0x229/0x911 [kvm]
 [<ffffffffa01c6ba9>] ? gfn_to_memslot+0x39/0xa0 [kvm]
 [<ffffffffa01c6c26>] ? mark_page_dirty+0x16/0x2e [kvm]
 [<ffffffffa01c6d6f>] ? kvm_write_guest_page+0x67/0x7f [kvm]
 [<ffffffff81066fbd>] ? local_clock+0x2a/0x3b
 [<ffffffffa01d52ce>] emulator_write_phys+0x46/0x54 [kvm]
 ......
Code:  Bad RIP value.
RIP  [<ffffffffa0172056>] 0xffffffffa0172056
 RSP <ffff880134f69a70>
CR2: ffffffffa0172056
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -3355,15 +3355,6 @@ int kvm_mmu_setup(struct kvm_vcpu *vcpu)
 	return init_kvm_mmu(vcpu);
 }
 
-void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
-{
-	ASSERT(vcpu);
-
-	destroy_kvm_mmu(vcpu);
-	free_mmu_pages(vcpu);
-	mmu_free_memory_caches(vcpu);
-}
-
 void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
 {
 	struct kvm_mmu_page *sp;
@@ -3662,4 +3653,16 @@ EXPORT_SYMBOL_GPL(kvm_mmu_get_spte_hierarchy);
 
 #ifdef CONFIG_KVM_MMU_AUDIT
 #include "mmu_audit.c"
+#else
+static void mmu_audit_disable(void) { }
 #endif
+
+void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
+{
+	ASSERT(vcpu);
+
+	destroy_kvm_mmu(vcpu);
+	free_mmu_pages(vcpu);
+	mmu_free_memory_caches(vcpu);
+	mmu_audit_disable();
+}