aidl: Suppress warnings on out-array

out-param arrays are considered harmful since the Java backend requires
them to be correctly allocated at caller site. But the only user of
android.hardware.identity is in C++, we can just ignore them.

Fixes: 179853403
Test: mma in hardware/interfaces/identity
Change-Id: Ib9b7ad895b3827c0888869a5b154696e3aff5624