init.rc: set fsck log permission on post-fs-data

Fixes: 130829745
Test: build and trigger fsck
      crosshatch:/ # ls -l /dev/fscklogs/log
      -rwxrwx--- 1 root system 1584 1970-04-08 14:48 /dev/fscklogs/log
Change-Id: Ifd0734e121d07b941a73d7cabde04928ce5e5c59