x86: coreboot: Add a boot script

Provide the user with a list of available boot options. Selecting one
causes it to be booted. Pressing <ESC> causes U-Boot to return to the
command-line prompt.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
2 files changed