LoongArch: KVM: Add stub for kvm_arch_vcpu_preempted_in_kernel()

Pause-Loop Exiting is not supported by LoongArch hardware, nor is pv
spinlock feature. So function kvm_vcpu_on_spin() is not used. Function
kvm_arch_vcpu_preempted_in_kernel() is defined as a stub function here
since it is only called by unused function kvm_vcpu_on_spin().

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: bibo-mao

arch/loongarch/kvm/vcpu.c

@@ -364,6 +364,11 @@ bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 	return false;
 }
 
+bool kvm_arch_vcpu_preempted_in_kernel(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
 vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
 {
 	return VM_FAULT_SIGBUS;