x86: chromebook_panther: Correct the image layout

This board does not have microcode but at present that is not supported
by Kconfig nor the binman image layout. Fix both of these.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 01ffaea..cbca69e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -594,8 +594,13 @@
           Various peripherals may fail to work.
 
 config HAVE_MICROCODE
-	bool
+	bool "Board requires a microcode binary"
 	default y if !FSP_VERSION2
+	help
+	  Enable this if the board requires microcode to be loaded on boot.
+	  Typically this is handed by the FSP for modern boards, but for
+	  some older boards, it must be programmed by U-Boot, and that form
+	  part of the image.
 
 config SMP
 	bool "Enable Symmetric Multiprocessing"