mediacodec: Add a couple 32-bit permissions

We add permissions for 'readlink' and 'open' for 32-bit targets.
These are used when grabbing bug reports, at least on some
32-bit devices.

Test: Tried this change on a 32-bit device that was getting fatal
aborts when taking bugreports, and confirm we no longer get fatal
aborts.
Bug: 132807384

Change-Id: I526217e9201d2a709baa2a6d9f078244578d678d