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: NBreno Lima <breno.lima@nxp.com>
Reviewed-by: NFabio Estevam <fabio.estevam@nxp.com>

arch/arm/cpu/armv7/mx6/Kconfig

@@ -217,6 +217,7 @@ config TARGET_UDOO
 config TARGET_UDOO_NEO
 	bool "UDOO Neo"
 	select SUPPORT_SPL
+	select MX6SX
 
 config TARGET_SAMTEC_VINING_2000
 	bool "samtec VIN|ING 2000"

configs/udoo_neo_defconfig

@@ -11,7 +11,7 @@ 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_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