KVM: remove kvm_arch_has_vcpu_debugfs()

There is no need for this function as all arches have to implement
kvm_arch_create_vcpu_debugfs() no matter what.  A #define symbol
let us actually simplify the code.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/s390/kvm/kvm-s390.c

@@ -2516,16 +2516,6 @@ out_err:
 	return rc;
 }
 
-bool kvm_arch_has_vcpu_debugfs(void)
-{
-	return false;
-}
-
-int kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu)
-{
-	return 0;
-}
-
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
 	VCPU_EVENT(vcpu, 3, "%s", "free cpu");