x86: Kconfig: Divide the target selection to vendor/model

Let arch/x86/Kconfig prompt board vendor first, then select
the board model under that vendor. This way arch/x86/Kconfig
only needs concern board vendor and leave the supported target
list to board/<vendor>/Kconfig.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

board/intel/Kconfig

@@ -0,0 +1,51 @@
+#
+# Copyright (C) 2015, Bin Meng <bmeng.cn@gmail.com>
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+if VENDOR_INTEL
+
+choice
+	prompt "Mainboard model"
+
+config TARGET_CROWNBAY
+	bool "Crown Bay"
+	help
+	  This is the Intel Crown Bay Customer Reference Board. It contains
+	  the Intel Atom Processor E6xx populated on the COM Express module
+	  with 1GB DDR2 soldered down memory and a carrier board with the
+	  Intel Platform Controller Hub EG20T, other system components and
+	  peripheral connectors for PCIe/SATA/USB/LAN/SD/UART/Audio/LVDS.
+
+config TARGET_GALILEO
+	bool "Galileo"
+	help
+	  This is the Intel Galileo board, which is the first in a family of
+	  Arduino-certified development and prototyping boards based on Intel
+	  architecture. It includes an Intel Quark SoC X1000 processor, a 32-bit
+	  single-core, single-thread, Intel Pentium processor instrunction set
+	  architecture (ISA) compatible, operating at speeds up to 400Mhz,
+	  along with 256MB DDR3 memory. It supports a wide range of industry
+	  standard I/O interfaces, including a full-sized mini-PCIe slot,
+	  one 100Mb Ethernet port, a microSD card slot, a USB host port and
+	  a USB client port.
+
+config TARGET_MINNOWMAX
+	bool "Minnowboard MAX"
+	help
+	  This is the Intel Minnowboard MAX. It contains an Atom E3800
+	  processor in a small form factor with Ethernet, micro-SD, USB 2,
+	  USB 3, SATA, serial console, some GPIOs 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/intel/crownbay/Kconfig"
+source "board/intel/galileo/Kconfig"
+source "board/intel/minnowmax/Kconfig"
+
+endif