Use copy_to_user() not put_user for struct timespec

Use copy_to_user() when copying a struct timespec to the guest -
put_user() cannot handle two long's in one go on a 64bit arch.
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Al Viro <viro@ftp.linux.org.uk>

drivers/lguest/hypercalls.c

@@ -295,6 +295,6 @@ void write_timestamp(struct lguest *lg)
 {
 	struct timespec now;
 	ktime_get_real_ts(&now);
-	if (put_user(now, &lg->lguest_data->time))
+	if (copy_to_user(&lg->lguest_data->time, &now, sizeof(struct timespec)))
 		kill_guest(lg, "Writing timestamp");
 }