Use actual consumed buffer length to call AParcel_unmarshal

Test: m binder_parcel_fuzzer &&
out/host/linux-x86/fuzz/x86_64/binder_parcel_fuzzer/binder_parcel_fuzzer
Bug: 264746958

Change-Id: I379d04b0e25d5f9f475352abb9a078542cb0eb5d
1 file changed