x86: dfi: Add option to select different config headers for baseboards

This patch adds the infrastructure to define different config headers
with different configurations and default environment for the baseboards
that can now be selected via Kconfig. The new configuration for the
theadorable-x86-dfi-bt700 is also added.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/board/dfi/Kconfig b/board/dfi/Kconfig
index d2a1d78..5488f68 100644
--- a/board/dfi/Kconfig
+++ b/board/dfi/Kconfig
@@ -8,10 +8,9 @@
 
 choice
 	prompt "Mainboard model"
-	optional
 
-config TARGET_DFI_BT700
-	bool "DFI BT700 BayTrail"
+config TARGET_Q7X_151_DFI_BT700
+	bool "DFI BT700 BayTrail on DFI Q7X-151 baseboard"
 	imply SCSI
 	help
 	  This is the DFI Q7X-151 baseboard equipped with the
@@ -23,6 +22,19 @@
 	  Note that PCIE_ECAM_BASE is set up by the FSP so the value used
 	  by U-Boot matches that value.
 
+config TARGET_THEADORABLE_X86_DFI_BT700
+	bool "DFI BT700 BayTrail on theadorable-x86 baseboard"
+	imply SCSI
+	help
+	  This is the theadorable-x86 baseboard equipped with the
+	  DFI BayTrail Bt700 SoM. It contains an Atom E3845 with
+	  Ethernet (in non-PCIe-x4 configuration), micro-SD, USB 2,
+	  USB 3, SATA, serial console and DisplayPort video out.
+	  It requires some binary blobs - see README.x86 for details.
+
+	  Note that PCIE_ECAM_BASE is set up by the FSP so the value used
+	  by U-Boot matches that value.
+
 endchoice
 
 source "board/dfi/dfi-bt700/Kconfig"