Add desc fields for neutron_router_interface

I found this confusing and wasted some time with it, so hopefully this
clears up the field meanings a bit for everyone else.

Change-Id: If2fac987162ae1e980e93288525d35906437b403

lib/puppet/type/neutron_router_interface.rb

@@ -11,29 +11,37 @@ Puppet::Type.newtype(:neutron_router_interface) do
   ensurable
 
   newparam(:name, :namevar => true) do
+    desc <<-EOT
+       The name is used to derive the names of the subnet and router,
+       using the format RouterName:SubnetName, for example to attach
+       Subnet1 to Router1 you should name this resource Router1:Subnet1
+    EOT
     newvalues(/^\S+:\S+$/)
   end
 
   newproperty(:id) do
+    desc 'interface id. Read Only.'
     validate do |v|
       raise(Puppet::Error, 'This is a read only property')
     end
   end
 
   newproperty(:router_name) do
+    desc 'router to which to attach this interface. Read Only. set with the name'
     validate do |v|
       raise(Puppet::Error, 'This is a read only property')
     end
   end
 
   newproperty(:subnet_name) do
+    desc 'subnet to which to attach this interface. Read Only. set with the name'
     validate do |v|
       raise(Puppet::Error, 'This is a read only property')
     end
   end
 
   newproperty(:port) do
-    desc 'An existing neutron port to which a rounter interface should be assigned'
+    desc 'An existing neutron port to which a router interface should be assigned'
   end
 
   autorequire(:service) do