kvargs: fix build with gcc 4.5.1

GCC 4.5.1 warns about an uninitialized pointer:
	error: 'ctx1' may be used uninitialized in this function

Signed-off-by: Min Cao <min.cao@intel.com>
Acked-by: Jijiang Liu <jijiang.liu@intel.com>
Tested-by: Waterman Cao <waterman.cao@intel.com>

lib/librte_kvargs/rte_kvargs.c

@@ -48,7 +48,9 @@ static int
 rte_kvargs_tokenize(struct rte_kvargs *kvlist, const char *params)
 {
 	unsigned i;
-	char *str, *ctx1, *ctx2;
+	char *str;
+	char *ctx1 = NULL;
+	char *ctx2 = NULL;
 
 	/* Copy the const char *params to a modifiable string
 	 * to pass to rte_strsplit