documentation/kernel-manual/kernel-how-to.xml: fix to step 3 and 4 of section 3.4.4

Added text after the sample bbappend file stating that the user needs
to update the KSRC assignment statement and also remove its comment.
Also they have to remove the comment from the SRC_URI line.

Changed the bitbake command in step 4 to use the linux-yocto-stable
file rather than the linux-yocto file.

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>

documentation/kernel-manual/kernel-how-to.xml

@@ -1111,6 +1111,11 @@ That's it. Configure and build.
      # SRC_URI = "git://${KSRC};nocheckout=1;branch=${KBRANCH},meta;name=machine,meta"
                     </literallayout>
                 </para>
+
+                <para>
+                    In the previous sample file you need to update and remove the comment from 
+                    the KSRC assignment and also remove the comment from the SRC_URI line.
+                </para>
                 
                 <para>
                     After doing that, select the machine in <filename>build/conf/local.conf</filename>:
@@ -1177,7 +1182,7 @@ That's it. Configure and build.
                     Then, modify the code there, using quilt to save the changes, and recompile until 
                     it works:
                     <literallayout class='monospaced'>
-     $ bitbake -c compile -f linux-yocto
+     $ bitbake -c compile -f linux-yocto-stable
                     </literallayout>
                 </para></listitem>