rust: hrtimer: add maintainer entry

Add Andreas Hindborg as maintainer for Rust `hrtimer` abstractions. Also
add Boqun Feng as reviewer.

Acked-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://lore.kernel.org/r/20250309-hrtimer-v3-v6-12-rc2-v12-13-73586e2bd5f1@kernel.org


Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>