Let MX35 and MX50 device tree support be built by default.

Generated by doing:

- Selected CONFIG_MACH_IMX35_DT and CONFIG_SOC_IMX50 via 'make menuconfig'
- make savedefconfig
- cp defconfig arch/arm/configs/imx_v6_v7_defconfig
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>