ARM: imx/imx31-dt: drop selecting USE_OF

since commit
	3e62af82 (ARM: imx: select USE_OF)
ARM_MXC already selects USE_OF, so there is no need to repeat it for
MACH_IMX31_DT
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/Kconfig

@@ -561,7 +561,6 @@ config MACH_BUG
 config MACH_IMX31_DT
 	bool "Support i.MX31 platforms from device tree"
 	select SOC_IMX31
-	select USE_OF
 	help
 	  Include support for Freescale i.MX31 based platforms
 	  using the device tree for discovery.