The following build warning is seen in tables.c:

  warning: implicit declaration of function 'memalign'

Add the missing header file to fix it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>