KVM: x86: Use this_cpu_ptr() in kvm_user_return_msr_cpu_online

Use this_cpu_ptr() instead of open coding the equivalent in
kvm_user_return_msr_cpu_online.
Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
Link: https://lore.kernel.org/r/87zfp96ojk.wl-me@linux.beautySigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/x86.c

@@ -413,8 +413,7 @@ EXPORT_SYMBOL_GPL(kvm_find_user_return_msr);
 
 static void kvm_user_return_msr_cpu_online(void)
 {
-	unsigned int cpu = smp_processor_id();
-	struct kvm_user_return_msrs *msrs = per_cpu_ptr(user_return_msrs, cpu);
+	struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs);
 	u64 value;
 	int i;