Mediaserver no longer appears, and maybe never did, need write
permission to sysfs files.
commit: 1de9c492 added auditing to
make sure this is the case, and such access has not been observed.
Remove the permissions and the associated auditallow rule to further
confine the mediaserver sandbox.

Bug: 22827371
Change-Id: I44ca1521b9791db027300aa84e54c074845aa735