uboot-imx

x86: Move table csum into separate file

We need the checksum function without all the other table functionality
soon, so let's split it out into its own C file.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>