tegra3-common: Fix smardimmer and mmcblk0p2 permissions

Fixes the following errors on boot.

E/STT:emmc(17113): emmc_open(): /dev/block/mmcblk0p2: Permission denied
E/STT:partition(17113): partition_open(): cannot find partition [WDM]!
E/        (17113): [Flash Calibration] : partition_open ["WDM"] failed, errno = 13 (Permission denied)! Use original cfg value.
E/HtcCameraHal(  151): [CAM] [Calibration] open file ["/data/factory_main.bin"] failed, errno = 13 (Permission denied)

E/hwcomposer(  148): /sys/class/graphics/fb0/device/smartdimmer/enable: open failed: Permission denied
E/hwcomposer(  148): Failed to set initial DIDIM status to disable

Change-Id: I98a32a39a66f88f7dff3a4ab1ada867aaabff568