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/dfi-bt700/Kconfig b/board/dfi/dfi-bt700/Kconfig
index 81a2575..4b6c3fc 100644
--- a/board/dfi/dfi-bt700/Kconfig
+++ b/board/dfi/dfi-bt700/Kconfig
@@ -1,5 +1,3 @@
-if TARGET_DFI_BT700
-
 config SYS_BOARD
 	default "dfi-bt700"
 
@@ -10,7 +8,8 @@
 	default "baytrail"
 
 config SYS_CONFIG_NAME
-	default "dfi-bt700"
+	default "dfi-bt700" if TARGET_Q7X_151_DFI_BT700
+	default "theadorable-x86-dfi-bt700" if TARGET_THEADORABLE_X86_DFI_BT700
 
 config SYS_TEXT_BASE
 	default 0xfff00000 if !EFI_STUB
@@ -24,8 +23,8 @@
 	select BOARD_EARLY_INIT_F
 	select BOARD_LATE_INIT
 	select SPI_FLASH_STMICRO
+	imply SPI_FLASH_SPANSION
+	imply SPI_FLASH_WINBOND
 
 config PCIE_ECAM_BASE
 	default 0xe0000000
-
-endif