x86: conga: 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-conga-qa3-e3845 is also added. Also the new defconfig
file for this new target is 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/congatec/Kconfig b/board/congatec/Kconfig
index ff5a1d8..fb341bf 100644
--- a/board/congatec/Kconfig
+++ b/board/congatec/Kconfig
@@ -24,6 +24,17 @@
 	  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_CONGA_QA3_E3845
+	bool "theadorable-x86 baseboard & conga-QA3/E3845"
+	help
+	  This is the theadorable-x86 baseboard board equipped with the
+	  conga-QA3/E3845-4G SoM. It contains an Atom E3845 with Ethernet,
+	  micro-SD, USB 2, USB 3, SATA, serial console and HDMI 1.3 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/congatec/conga-qeval20-qa3-e3845/Kconfig"