Add additional comments to the Zynq lwIP demo.

git-svn-id: http://svn.code.sf.net/p/freertos/code/trunk@2259 1d2547de-c912-0410-9cb9-b8ca96c0e9e2
Simplify the assert that checks if a non-ISR safe function is called from an ISR in the GCC Cortex-A9 port.

git-svn-id: http://svn.code.sf.net/p/freertos/code/trunk@2260 1d2547de-c912-0410-9cb9-b8ca96c0e9e2