kvm: Return -ENODEV from update_persistent_clock

kvm does not support setting the RTC, so the correct result is -ENODEV.
Returning -1 will cause sync_cmos_clock to keep trying to set the RTC
every second.
Signed-off-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kernel/kvmclock.c

@@ -79,7 +79,7 @@ static void kvm_get_wallclock(struct timespec *now)
 
 static int kvm_set_wallclock(const struct timespec *now)
 {
-	return -1;
+	return -ENODEV;
 }
 
 static u64 kvm_clock_read(void)