ARM: imx_v6_v7_defconfig: enable option CONFIG_LOCALVERSION_AUTO

Option CONFIG_LOCALVERSION_AUTO is quite helpful to tell kernel version.
I do not see any reason why we should unset it.  Let's remove the unset
to have it enabled.
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

arch/arm/configs/imx_v6_v7_defconfig

-# CONFIG_LOCALVERSION_AUTO is not set
 CONFIG_KERNEL_LZO=y
 CONFIG_SYSVIPC=y
 CONFIG_NO_HZ=y