mx6sx: Add initial support for UDOO Neo Board

UDOO Neo Board is a development board from Seco that has three models:
 - UDOO Neo Basic
 - UDOO Neo Basic Kick Starter
 - UDOO Neo Extended
 - UDOO Neo Full

All versions are based on the i.MX6 SoloX processor.

For more details about the UDOO Neo board, please refer to:
http://www.udoo.org/udoo-neo/

This work is based on a previous commit of Francesco Montefoschi
<francesco.monte@gmail.com>:
https://github.com/fmntf/u-boot/commit/877b71184a5105e708024f232d36aed574961844

Only tested on the UDOO Neo Full board.

Signed-off-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
diff --git a/configs/udoo_neo_defconfig b/configs/udoo_neo_defconfig
new file mode 100644
index 0000000..3304afb
--- /dev/null
+++ b/configs/udoo_neo_defconfig
@@ -0,0 +1,30 @@
+CONFIG_ARM=y
+CONFIG_ARCH_MX6=y
+CONFIG_SPL_GPIO_SUPPORT=y
+CONFIG_SPL_LIBCOMMON_SUPPORT=y
+CONFIG_SPL_LIBGENERIC_SUPPORT=y
+CONFIG_TARGET_UDOO_NEO=y
+CONFIG_SPL_EXT_SUPPORT=y
+CONFIG_SPL_LIBDISK_SUPPORT=y
+CONFIG_SPL_MMC_SUPPORT=y
+CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_ENV_SUPPORT=y
+CONFIG_SPL_WATCHDOG_SUPPORT=y
+CONFIG_SPL=y
+CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg,MX6SX"
+CONFIG_HUSH_PARSER=y
+CONFIG_CMD_BOOTZ=y
+# CONFIG_CMD_IMLS is not set
+# CONFIG_CMD_FLASH is not set
+CONFIG_CMD_MMC=y
+CONFIG_CMD_GPIO=y
+# CONFIG_CMD_SETEXPR is not set
+# CONFIG_CMD_DHCP=y
+CONFIG_CMD_CACHE=y
+CONFIG_CMD_TIME=y
+CONFIG_CMD_EXT2=y
+CONFIG_CMD_EXT4=y
+CONFIG_CMD_EXT4_WRITE=y
+CONFIG_CMD_FAT=y
+CONFIG_CMD_FS_GENERIC=y
+CONFIG_OF_LIBFDT=y