x86: link: Add a config for 64-bit U-Boot

Add a new board config which uses 64-bit U-Boot. This is not fully
functional but is it a start. Missing features:

- SDRAM sizing
- Booting linux
- EFI support
- SCSI device init
(and others)

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/board/google/Kconfig b/board/google/Kconfig
index 7ba73a2..e56c026 100644
--- a/board/google/Kconfig
+++ b/board/google/Kconfig
@@ -22,6 +22,13 @@
 	  and it provides a 2560x1700 high resolution touch-enabled LCD
 	  display.
 
+config TARGET_CHROMEBOOK_LINK64
+	bool "Chromebook link 64-bit"
+	help
+	  This is the Chromebook Pixel released in 2013. With this config
+	  U-Boot is built as a 64-bit binary. This allows testing while this
+	  feature is being completed.
+
 config TARGET_CHROMEBOX_PANTHER
 	bool "Chromebox panther (not available)"
 	select n