libbinder_rs: add SerializeArray for Option<SpIBinder>

SerializeArray was implemented for Option<&SpIBinder>. When IBinder[] is
passed as out parameter, we need Option<SpIBinder> as well.

Bug: 151817759
Test: aidl_integration_test
Change-Id: I10f54f091fb546eec0ddbed677a979359451e9d6
1 file changed