bootstd: cros: Add ARM support

Support booting ChromiumOS on ARM devices using FIT. Add an entry into the
boot implementation which does not require a command line. This can be
expanded over time as the bootm code is refactored.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/Kconfig b/boot/Kconfig
index b00d7a8..5e2d428 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -464,8 +464,8 @@
 
 config BOOTMETH_CROS
 	bool "Bootdev support for Chromium OS"
-	depends on X86 || SANDBOX
-	default y
+	depends on X86 || ARM || SANDBOX
+	default y if !ARM
 	help
 	  Enables support for booting Chromium OS using bootdevs. This uses the
 	  kernel A slot and obtains the kernel command line from the parameters