KVM: x86: remove unused last_kernel_ns variable

Remove unused last_kernel_ns variable.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -444,7 +444,6 @@ struct kvm_vcpu_arch {
 	} st;
 
 	u64 last_guest_tsc;
-	u64 last_kernel_ns;
 	u64 last_host_tsc;
 	u64 tsc_offset_adjustment;
 	u64 this_tsc_nsec;

arch/x86/kvm/x86.c

@@ -1581,7 +1581,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 	/* With all the info we got, fill in the values */
 	vcpu->hv_clock.tsc_timestamp = tsc_timestamp;
 	vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset;
-	vcpu->last_kernel_ns = kernel_ns;
 	vcpu->last_guest_tsc = tsc_timestamp;
 
 	/*