ref-manual: Added links for do_image and do_image_complete tasks

In the "Image Generation" section, I was referencing these tasks
and did not have any cross-link to the actual tasks.  I added them.

(From yocto-docs rev: da480933c59ddc3fe9fe4a881d4d0e21038a999b)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-development-environment.xml

@@ -2230,7 +2230,9 @@
 
             <para>
                 After the root filesystem is built, processing begins on
-                the image through the <filename>do_image</filename> task.
+                the image through the
+                <link linkend='ref-tasks-image'><filename>do_image</filename></link>
+                task.
                 The build system runs any pre-processing commands as defined
                 by the
                 <link linkend='var-IMAGE_PREPROCESS_COMMAND'><filename>IMAGE_PREPROCESS_COMMAND</filename></link>
@@ -2254,7 +2256,8 @@
 
             <para>
                 The final task involved in image creation is the
-                <filename>do_image_complete</filename> task.
+                <link linkend='ref-tasks-image-complete'><filename>do_image_complete</filename></link>
+                task.
                 This task completes the image by applying any image
                 post processing as defined through the
                 <link linkend='var-IMAGE_POSTPROCESS_COMMAND'><filename>IMAGE_POSTPROCESS_COMMAND</filename></link>