x86: doc: Update the list of supported Chromebooks

One is missing, so add it. Also mention the SoC used in each.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/doc/arch/x86.rst b/doc/arch/x86.rst
index 725a1ae..89d3e7b 100644
--- a/doc/arch/x86.rst
+++ b/doc/arch/x86.rst
@@ -25,12 +25,13 @@
    - Bayley Bay CRB
    - Cherry Hill CRB
    - Congatec QEVAL 2.0 & conga-QA3/E3845
+   - Coral (Apollo Lake - Chromebook 2017)
    - Cougar Canyon 2 CRB
    - Crown Bay CRB
    - Galileo
-   - Link (Chromebook Pixel)
+   - Link (Ivy Bridge - Chromebook Pixel)
    - Minnowboard MAX
-   - Samus (Chromebook Pixel 2015)
+   - Samus (Broadwell - Chromebook Pixel 2015)
    - QEMU x86 (32-bit & 64-bit)
 
 As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit