common: Label and allow init to write to I/O sched tuning nodes

* LineageOS/android_system_sepolicy@0e3235f45d removed open, read,
  and write for init to general sysfs types. Our init scripts do
  fancy things with these nodes, so a specific type is necessary
  to allow such fancy things to happen in Pie+.

Change-Id: I15d8913ddf9758403e01f85c89ee326626094401