MAINTAINERS: add entry for Rust dma mapping helpers device driver API

Add an entry for the Rust dma mapping helpers abstractions.

Nacked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@gmail.com>
Link: https://lore.kernel.org/r/20250317185345.2608976-5-abdiel.janulgue@gmail.com


Signed-off-by: Miguel Ojeda <ojeda@kernel.org>