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/usb.c b/common/usb.c
index fbaf8ec..700bfc3 100644
--- a/common/usb.c
+++ b/common/usb.c
@@ -29,6 +29,7 @@
 #include <common.h>
 #include <command.h>
 #include <dm.h>
+#include <memalign.h>
 #include <asm/processor.h>
 #include <linux/compiler.h>
 #include <linux/ctype.h>