KVM: vmx: delete meaningless vmx_decache_cr0_guest_bits() declaration

The function vmx_decache_cr0_guest_bits() is only called below its
implementation. So this is meaningless and should be removed.
Signed-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -1428,8 +1428,6 @@ static bool emulation_required(struct kvm_vcpu *vcpu)
 	return emulate_invalid_guest_state && !guest_state_valid(vcpu);
 }
 
-static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu);
-
 unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);