ANDROID: rust_binder: update prio_state on nested reply

When replying to a nested transaction, the prio_state should be updated
to pending. Otherwise the thread isn't restored to the parent
transaction's priority.

Fixes: dac7c66bc912 ("ANDROID: rust_binder: move Rust Binder in preparation for GKI module")
Change-Id: I593fca439318bc8257d4f2891ea889c1c8d42135
Signed-off-by: Alice Ryhl <aliceryhl@google.com>