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/boot/Kconfig b/boot/Kconfig
index c8b8f36..b424265 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -463,6 +463,17 @@
 	  EFI bootmgr, since they take full control over which bootdevs are
 	  selected to boot.
 
+config BOOTMETH_CROS
+	bool "Bootdev support for Chromium OS"
+	depends on X86 || SANDBOX
+	default y
+	help
+	  Enables support for booting Chromium OS using bootdevs. This uses the
+	  kernel A slot and obtains the kernel command line from the parameters
+	  provided there.
+
+	  Note that only x86 devices are supported at present.
+
 config BOOTMETH_EXTLINUX
 	bool "Bootdev support for extlinux boot"
 	select PXE_UTILS