x86: slimbootloader: Convert to text environment

Use the common include along with some additions.

Drop everything from the config.h file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> # Intel Edison
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[Drop common env from slimbootloader.env]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2 files changed