mm: rust: add MEMORY MANAGEMENT [RUST]

We have introduced Rust bindings for core mm abstractions as part of this
series, so add an entry in MAINTAINERS to be explicit about who maintains
this.

Patches are anticipated to be taken through the mm tree as usual with
other mm code.

Link: https://rust-for-linux.com/rust-kernel-policy#how-is-rust-introduced-in-a-subsystem
Link: https://lore.kernel.org/all/33e64b12-aa07-4e78-933a-b07c37ff1d84@lucifer.local/
Link: https://lkml.kernel.org/r/20250408-vma-v16-9-d8b446e885d9@google.com


Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: Björn Roy Baron <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jann Horn <jannh@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Trevor Gross <tmgross@umich.edu>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>