configs: add nitrogen6sx_defconfig for Boundary Devices SoloX board

This board is using the exact same kernel and u-boot revision as the
Nitrogen6x. They also share the same u-boot "autoboot" script.

The differences between the two configurations are:
- getty port is ttymxc0 instead of ttymxc1
- uImage load address is 0x80008000
- different device tree

http://boundarydevices.com/product/nit6_solox-imx6/

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

configs/nitrogen6sx_defconfig

@@ -0,0 +1,37 @@
+# architecture
+BR2_arm=y
+BR2_cortex_a9=y
+
+# system
+BR2_TARGET_GENERIC_GETTY=y
+BR2_TARGET_GENERIC_GETTY_PORT="ttymxc0"
+BR2_ROOTFS_POST_BUILD_SCRIPT="board/boundarydevices/nitrogen6x/post-build.sh"
+BR2_PACKAGE_HOST_UBOOT_TOOLS=y
+
+# filesystem
+BR2_TARGET_ROOTFS_EXT2=y
+BR2_TARGET_ROOTFS_EXT2_2r1=y
+
+# Lock headers to match kernel
+BR2_KERNEL_HEADERS_VERSION=y
+BR2_DEFAULT_KERNEL_VERSION="3.14.28"
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_3_14=y
+
+# bootloader
+BR2_TARGET_UBOOT=y
+BR2_TARGET_UBOOT_BOARDNAME="nitrogen6sx"
+BR2_TARGET_UBOOT_FORMAT_IMX=y
+BR2_TARGET_UBOOT_CUSTOM_TARBALL=y
+# Last version of branch boundary-v2015.07
+BR2_TARGET_UBOOT_CUSTOM_TARBALL_LOCATION="http://github.com/boundarydevices/u-boot-imx6/tarball/5115a9e/u-boot-5115a9e.tar.gz"
+
+# kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
+# Last version of branch boundary-imx_3.14.28_1.0.0_ga
+BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION="https://github.com/boundarydevices/linux-imx6/tarball/3417c66/linux-imx6-3417c66.tar.gz"
+BR2_LINUX_KERNEL_DEFCONFIG="nitrogen6x"
+BR2_LINUX_KERNEL_INSTALL_TARGET=y
+BR2_LINUX_KERNEL_UIMAGE_LOADADDR="0x80008000"
+BR2_LINUX_KERNEL_DTS_SUPPORT=y
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx6sx-nitrogen6sx"