udoo_neo: Move MX6SX configuration to Kconfig

It's not necessary to define the processor in the defconfig file.

The preferred method to select the SoC is via Kconfig file.

Signed-off-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
diff --git a/arch/arm/cpu/armv7/mx6/Kconfig b/arch/arm/cpu/armv7/mx6/Kconfig
index 5a8c7bf..cca8a87 100644
--- a/arch/arm/cpu/armv7/mx6/Kconfig
+++ b/arch/arm/cpu/armv7/mx6/Kconfig
@@ -217,6 +217,7 @@
 config TARGET_UDOO_NEO
 	bool "UDOO Neo"
 	select SUPPORT_SPL
+	select MX6SX
 
 config TARGET_SAMTEC_VINING_2000
 	bool "samtec VIN|ING 2000"
diff --git a/configs/udoo_neo_defconfig b/configs/udoo_neo_defconfig
index 3304afb..f88820c 100644
--- a/configs/udoo_neo_defconfig
+++ b/configs/udoo_neo_defconfig
@@ -11,7 +11,7 @@
 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_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg"
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMLS is not set