test: fix build with GCC 11

[ upstream commit 50eea2b ]

GCC 11 complains that 'a' is uninitialized.

../dpdk/app/test/test_prefetch.c: In function 'test_prefetch':
../dpdk/app/test/test_prefetch.c:25:9:
error: 'a' may be used uninitialized [-Werror=maybe-uninitialized]
   25 |         rte_prefetch0(&a);
      |         ^~~~~~~~~~~~~~~~~

Fix by initializing 'a'.

Bugzilla ID: 714
Fixes: af75078 ("first public release")

Reported-by: Ali Alnubani <alialnu@nvidia.com>
Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Tested-by: Ali Alnubani <alialnu@nvidia.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>

app/test/test_prefetch.c

@@ -20,7 +20,7 @@
 static int
 test_prefetch(void)
 {
-	int a;
+	int a = 0;
 
 	rte_prefetch0(&a);
 	rte_prefetch1(&a);