unit: Fix compiler warning

unit/test-ie.c: In function ‘ie_test’:
unit/test-ie.c:70:2: error: comparison between signed and unsigned
integer expressions [-Werror=sign-compare]

unit/test-ie.c

@@ -49,7 +49,7 @@ static void ie_test(const void *data)
 	const struct test_data *test = data;
 	struct ie_tlv_iter iter;
 	struct ie *ie;
-	int count = 0, pos = 0;
+	unsigned int count = 0, pos = 0;
 
 	ie_tlv_iter_init(&iter, test->buf, test->len);