Minor changes to the LinkAddress API docs.

1. Rename getNetworkPrefixLength to getPrefixLength. Update all
   callers in frameworks/base and add a shim method and a TODO
   for the rest.
2. @hide isSameAddressAs. It doesn't add much, and it's just
   one-liner that callers can implement if they want.
3. Fix the alignment of the initial paragraph (<ul> should have
   been </ul>).
4. Remove the documentation that talks about creating
   LinkAddresses, since there's no public API for creating them.

With these changes I think LinkAddress is fine as a public API.

Bug: 15142362
Change-Id: Iaf3b1db577745bb68a9e1dd7f96d666dd3f3ec7c
(cherry picked from commit 9ab53650cfcd91a2a151b44b3fd1381841f76269)
diff --git a/services/core/java/com/android/server/ConnectivityService.java b/services/core/java/com/android/server/ConnectivityService.java
index bd45761..de99aec 100644
--- a/services/core/java/com/android/server/ConnectivityService.java
+++ b/services/core/java/com/android/server/ConnectivityService.java
@@ -1669,7 +1669,7 @@
                         continue;
                     }
 
-                    int prefix = destination.getNetworkPrefixLength();
+                    int prefix = destination.getPrefixLength();
                     InetAddress addrMasked = NetworkUtils.getNetworkPart(address, prefix);
                     InetAddress destMasked = NetworkUtils.getNetworkPart(destination.getAddress(),
                             prefix);