x86: Add debugging to table writing

Writing tables is currently pretty opaque. Add a bit of debugging to the
process so we can see what tables are written and where they start/end in
memory.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>