Move ALLOC_CACHE_ALIGN_BUFFER() to the new memalign.h header

Now that we have a new header file for cache-aligned allocation, we should
move the stack-based allocation macro there also.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/env_ubi.c b/common/env_ubi.c
index 77bbfa6..e0dc5af 100644
--- a/common/env_ubi.c
+++ b/common/env_ubi.c
@@ -11,6 +11,7 @@
 #include <environment.h>
 #include <errno.h>
 #include <malloc.h>
+#include <memalign.h>
 #include <search.h>
 #include <ubi_uboot.h>
 #undef crc32