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/drivers/block/ahci.c b/drivers/block/ahci.c
index 0d19dd2..82c6843 100644
--- a/drivers/block/ahci.c
+++ b/drivers/block/ahci.c
@@ -15,6 +15,7 @@
 #include <asm/errno.h>
 #include <asm/io.h>
 #include <malloc.h>
+#include <memalign.h>
 #include <scsi.h>
 #include <libata.h>
 #include <linux/ctype.h>