ARM: imx_v6_v7_defconfig: Select CONFIG_DEBUG_FS

CONFIG_DEBUG_FS is a very useful debug option as it allow us to access key
data such as the clock tree, for example:

mount -t debugfs debugfs /sys/kernel/debug
cat /sys/kernel/debug/clk/clk_summary
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -283,6 +283,7 @@ CONFIG_NLS_ASCII=y
 CONFIG_NLS_ISO8859_1=y
 CONFIG_NLS_ISO8859_15=m
 CONFIG_NLS_UTF8=y
+CONFIG_DEBUG_FS=y
 CONFIG_MAGIC_SYSRQ=y
 # CONFIG_SCHED_DEBUG is not set
 CONFIG_PROVE_LOCKING=y