helpers: add io_uring_posix_memalign helper

add io_uring_posix_memalign helper, and replace
all posix_memalign() with io_uring_posix_memalign()
in all tests.

Signed-off-by: Zhiqiang Liu <[email protected]>
diff --git a/test/helpers.c b/test/helpers.c
index 7acf184..83ed3e5 100644
--- a/test/helpers.c
+++ b/test/helpers.c
@@ -17,3 +17,14 @@
 	assert(ret);
 	return ret;
 }
+
+
+/*
+ * Helper for allocating size bytes aligned on a boundary.
+ */
+void io_uring_posix_memalign(void **memptr, size_t alignment, size_t size)
+{
+	int ret;
+	ret = posix_memalign(memptr, alignment, size);
+	assert(!ret);
+}