ARM: imx53: support device tree boot only

With device tree kernel provides the equal support as those imx53 board
files, it's time to remove the board files and get imx53 support device
tree only.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/configs/imx_v6_v7_defconfig b/arch/arm/configs/imx_v6_v7_defconfig
index 400ef34..565132d 100644
--- a/arch/arm/configs/imx_v6_v7_defconfig
+++ b/arch/arm/configs/imx_v6_v7_defconfig
@@ -32,7 +32,7 @@
 CONFIG_MACH_IMX51_DT=y
 CONFIG_MACH_MX51_3DS=y
 CONFIG_MACH_EUKREA_CPUIMX51SD=y
-CONFIG_MACH_IMX53_DT=y
+CONFIG_SOC_IMX53=y
 CONFIG_SOC_IMX6Q=y
 CONFIG_MXC_PWM=y
 CONFIG_SMP=y