ospf6d: Support for 'clear ipv6 ospf6 interface [ifname]

Clear interface commands for ospfv3.  Allow the user
to clear all peers out the specified interface.

Signed-off-by: Vipin Kumar <vipin@cumulusnetworks.com>
diff --git a/ospf6d/ospf6d.c b/ospf6d/ospf6d.c
index fa84d0a..f9b0322 100644
--- a/ospf6d/ospf6d.c
+++ b/ospf6d/ospf6d.c
@@ -1790,6 +1790,8 @@
   install_element_ospf6_debug_abr ();
   install_element_ospf6_debug_flood ();
 
+  install_element_ospf6_clear_interface ();
+
   install_element (VIEW_NODE, &show_version_ospf6_cmd);
 
   install_element (VIEW_NODE, &show_ipv6_ospf6_border_routers_cmd);