fix typo in guide for nested kvm

Change-Id: Ie103a097830401248c75fcb16d4dd746bbbb7288
Signed-off-by: Hiroshi Miura <miurahr@nttdata.co.jp>
diff --git a/doc/source/guides/devstack-with-nested-kvm.rst b/doc/source/guides/devstack-with-nested-kvm.rst
index b35492e..c652bac 100644
--- a/doc/source/guides/devstack-with-nested-kvm.rst
+++ b/doc/source/guides/devstack-with-nested-kvm.rst
@@ -88,7 +88,7 @@
     parm:           nested:int
 
 To make the above value persistent across reboots, add an entry in
-/etc/modprobe.ddist.conf so it looks as below::
+/etc/modprobe.d/dist.conf so it looks as below::
 
     cat /etc/modprobe.d/dist.conf
     options kvm-amd nested=y