lguest: update help text.

We now add about 10k, not 6k, when lguest support is compiled in.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

arch/x86/lguest/Kconfig

@@ -8,7 +8,7 @@ config LGUEST_GUEST
 	help
 	  Lguest is a tiny in-kernel hypervisor.  Selecting this will
 	  allow your kernel to boot under lguest.  This option will increase
-	  your kernel size by about 6k.  If in doubt, say N.
+	  your kernel size by about 10k.  If in doubt, say N.
 
 	  If you say Y here, make sure you say Y (or M) to the virtio block
 	  and net drivers which lguest needs.