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/configs/chromebox_panther_defconfig b/configs/chromebox_panther_defconfig
index d559e03..701edf0 100644
--- a/configs/chromebox_panther_defconfig
+++ b/configs/chromebox_panther_defconfig
@@ -8,7 +8,9 @@
 CONFIG_VENDOR_GOOGLE=y
 CONFIG_TARGET_CHROMEBOX_PANTHER=y
 CONFIG_HAVE_MRC=y
+# CONFIG_HAVE_MICROCODE is not set
 CONFIG_HAVE_VGA_BIOS=y
+CONFIG_X86_OFFSET_U_BOOT=0xffa00000
 CONFIG_FIT=y
 CONFIG_BOOTSTAGE=y
 CONFIG_BOOTSTAGE_REPORT=y