x86: Make QEMU the default vendor

Now that we have QEMU support, make it the default vendor in the
'make menuconfig' screen.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/coreboot-x86_defconfig b/configs/coreboot-x86_defconfig
index 9bed74c..bd1068e 100644
--- a/configs/coreboot-x86_defconfig
+++ b/configs/coreboot-x86_defconfig
@@ -1,4 +1,5 @@
 CONFIG_X86=y
+CONFIG_VENDOR_COREBOOT=y
 CONFIG_TARGET_COREBOOT=y
 CONFIG_CMD_NET=y
 CONFIG_OF_CONTROL=y