x86: Store the coreboot table address in global_data

At present this information is used to locate and parse the tables but is
not stored. Store it so that we can display it to the user, e.g. with the
'bdinfo' command.

Note that now the GD_FLG_SKIP_LL_INIT flag is set in get_coreboot_info(),
so it is always set when booting from coreboot.

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>