fix(xilinx): follow MISRA-C standards for condition check

As per the MISRA-C standards, there should be proc == NULL not just
!proc.

Fix the same.

Change-Id: I0e7650c09b045882a0235869d7ef9fca27f96d9a
Signed-off-by: Ronak Jain <ronak.jain@amd.com>