bootstd: Add a simple bootmeth for ChromiumOS

It is possible to boot x86-based ChromeOS machines by parsing a table and
locating the kernel and command line. Add a bootmeth for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/configs/tools-only_defconfig b/configs/tools-only_defconfig
index 2bc3bd9..3f588ea 100644
--- a/configs/tools-only_defconfig
+++ b/configs/tools-only_defconfig
@@ -10,6 +10,7 @@
 CONFIG_TIMESTAMP=y
 CONFIG_FIT_SIGNATURE=y
 # CONFIG_BOOTSTD_FULL is not set
+# CONFIG_BOOTMETH_CROS is not set
 # CONFIG_BOOTMETH_VBE is not set
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="run distro_bootcmd"