NetworkPkg/Ip6Dxe: Fix typo in comment

An extra 's' slipped into the 'processing' word.
Drop it to fix the typo.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Siyuan Fu <siyuan.fu@intel.com>
Signed-off-by: Philippe Mathieu-Daude <philmd@redhat.com>

NetworkPkg/Ip6Dxe/Ip6Option.c

@@ -158,7 +158,7 @@ Ip6IsNDOptionValid (
       //
       // Check the length of Ip6OptionEtherSource, Ip6OptionEtherTarget, and
       // Ip6OptionRedirected here. For unrecognized options, silently ignore
-      // and continue processsing the message.
+      // and continue processing the message.
       //
       if (Length == 0) {
         return FALSE;