MAINTAINERS: add Benno Lossin as Rust reviewer

Benno has been involved with the Rust for Linux project for
the better part of a year now. He has been working on solving
the safe pinned initialization problem [1], which resulted in
the pin-init API patch series [2] that allows to reduce the
need for `unsafe` code in the kernel. He is also working on
the field projection RFC for Rust [3] to bring pin-init as
a language feature.

His expertise with the language will be very useful to have
around in the future if Rust grows within the kernel, thus
add him to the `RUST` entry as reviewer.

Link: https://rust-for-linux.com/the-safe-pinned-initialization-problem [1]
Link: https://lore.kernel.org/rust-for-linux/20230408122429.1103522-1-y86-dev@protonmail.com/ [2]
Link: rust-lang/rfcs#3318 [3]
Cc: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alex Gaynor <alex.gaynor@gmail.com>
Link: https://lore.kernel.org/r/20230412221823.830135-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

MAINTAINERS

@@ -18238,6 +18238,7 @@ M:	Wedson Almeida Filho <wedsonaf@gmail.com>
 R:	Boqun Feng <boqun.feng@gmail.com>
 R:	Gary Guo <gary@garyguo.net>
 R:	Björn Roy Baron <bjorn3_gh@protonmail.com>
+R:	Benno Lossin <benno.lossin@proton.me>
 L:	rust-for-linux@vger.kernel.org
 S:	Supported
 W:	https://github.com/Rust-for-Linux/linux