MAINTAINERS: add Onur Özkan as Rust reviewer

MAINTAINERS: add Onur Özkan as Rust reviewer

Onur has been involved with the Rust for Linux project for a year now. He
works on the Tyr driver for Arm Mali GPUs [1] and has been driving the
`ww_mutex` series and the SRCU abstractions, as well as improving the
core Rust support in several areas.

In addition, he is already a reviewer of the `RUST [SYNC]` entry and has
been involved with upstream Rust -- for instance, he led the bootstrap
team for two years.

His expertise with the language and its toolchain will be very useful to
have around in the future. Thus add him to the `RUST` entry as reviewer.

Link: https://rust-for-linux.com/tyr-gpu-driver
Acked-by: Onur Özkan <work@onurozkan.dev>
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260611055538.61425-4-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>