Limit values of data position in fuzzer

Negative values for data position leads to crashes in native code.
Limit domain to positive values only.

Test: m java_binder_parcel_fuzzer && ./jazzer_helper.sh --fuzz_target java_binder_parcel_fuzzer --target_class parcelfuzzer.ParcelFuzzer
Bug: 264673355
Change-Id: I5ce13560c30f96a8562b0b3c0fe98e1c1d7318ab