Change the priorities used by the RX/RSK/IAR demo application to ensure they can...

Change the priorities used by the RX/RSK/IAR demo application to ensure they can be used when configASSERT() is defined.  Previously the priorities meant assert would have been called because one of the priorities used was above ( configMAX_PRIORITIES - 1 ).

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@1328 1d2547de-c912-0410-9cb9-b8ca96c0e9e2