examples/ip_pipeline: fix build with GCC 13

[ upstream commit aae10e97710eb3b6a43a61e733ca0bbff47ab0c4 ]

Fix the following build issue by initializing req to NULL for
the local variable.

In function 'thread_msg_handle', inlined from 'thread_main' at
../examples/ip_pipeline/thread.c:3130:6:
../examples/ip_pipeline/thread.c:535:20: warning: 'req' may be used
uninitialized [-Wmaybe-uninitialized]
  535 |                 if (req == NULL)
      |                    ^
../examples/ip_pipeline/thread.c: In function 'thread_main':
../examples/ip_pipeline/thread.c:433:32: note: 'req' was declared here
  433 |         struct thread_msg_req *req;

Bugzilla ID: 1220
Fixes: a8bd581 ("examples/ip_pipeline: add thread runtime")

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Tested-by: Ali Alnubani <alialnu@nvidia.com>
Tested-by: Daxue Gao <daxuex.gao@intel.com>

examples/ip_pipeline/thread.c

@@ -432,7 +432,7 @@ thread_pipeline_disable(uint32_t thread_id,
 static inline struct thread_msg_req *
 thread_msg_recv(struct rte_ring *msgq_req)
 {
-	struct thread_msg_req *req;
+	struct thread_msg_req *req = NULL;
 
 	int status = rte_ring_sc_dequeue(msgq_req, (void **) &req);