ref-manual: Updated the SDK figure.

Added the SDKPATH variable to figure.  It was missing.
Also, had to adjust the display parameters to get it to
display decently.

(From yocto-docs rev: 4862288ab4675051ec6fc93927839da7eb3634b6)

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

documentation/ref-manual/closer-look.xml

@@ -1280,7 +1280,7 @@
             the output labeled "Application Development SDK" represents an
             SDK.
             This section is going to take a closer look at this output:
-            <imagedata fileref="figures/sdk.png" align="center" width="5in" depth="4in" />
+            <imagedata fileref="figures/sdk.png" align="center" width="6in" depth="5in" scalefit="100" />
         </para>
 
         <para>