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/net/e1000.c b/drivers/net/e1000.c
index 7b830ff..2ba03ed 100644
--- a/drivers/net/e1000.c
+++ b/drivers/net/e1000.c
@@ -32,6 +32,7 @@
 #include <common.h>
 #include <dm.h>
 #include <errno.h>
+#include <memalign.h>
 #include <pci.h>
 #include "e1000.h"