documentation: poky-ref-manual - change support to opkg from ipkg

We haven't supported ipkg for some time now - it was replaced by opkg
(whilst still using the ipk package format).

(From yocto-docs rev: 07b3dd9a73be25f31c919ed750ca320c7507eff0)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/poky-ref-manual/faq.xml

@@ -166,7 +166,7 @@
         <answer>
             <para>
                 The OpenEmbedded build system can build packages in various formats such as
-                <filename>ipk</filename> for <filename>ipkg</filename>/<filename>opkg</filename>, 
+                <filename>ipk</filename> for <filename>opkg</filename>, 
                 Debian package (<filename>.deb</filename>), or RPM. 
                 The packages can then be upgraded using the package tools on the device, much like 
                 on a desktop distribution such as Ubuntu or Fedora.

documentation/poky-ref-manual/ref-variables.xml

@@ -114,8 +114,8 @@
             <glossdef>
                 <para>
                     A list of packages not to install despite being recommended by a recipe.
-                    Support for this variable exists only for images that use the 
+                    Support for this variable exists only when using the 
-                    <filename>ipkg</filename> packaging system.
+                    <filename>ipk</filename> packaging backend.
                 </para>
             </glossdef>
         </glossentry>