x86: Move table csum into separate header

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

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