lguest: Point to the right directory for the lguest launcher

The code was moved in 07fe9977 but
the comment was not updated. The reference in drivers/vhost/vhost.c
is left alone as it is historic.
Signed-off-by: Holger Hans Peter Freyther <holger@moiji-mobile.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

arch/x86/lguest/boot.c

@@ -7,8 +7,7 @@
  * kernel and insert a module (lg.ko) which allows us to run other Linux
  * kernels the same way we'd run processes.  We call the first kernel the Host,
  * and the others the Guests.  The program which sets up and configures Guests
- * (such as the example in Documentation/virtual/lguest/lguest.c) is called the
- * Launcher.
+ * (such as the example in tools/lguest/lguest.c) is called the Launcher.
  *
  * Secondly, we only run specially modified Guests, not normal kernels: setting
  * CONFIG_LGUEST_GUEST to "y" compiles this file into the kernel so it knows