MAINTAINERS: Update the DMA Rust entry

Update the DMA Rust maintainers entry in the following two aspects:

  (1) Change Abdiel's entry to 'Reviewer'.

  (2) Take patches through the driver-core tree.

Abdiel won't do any more maintainer work on the DMA (or scatterlist)
infrastructure, but he'd like to be kept in the loop, hence change is
entry to 'R:'.

Analogous to [1], the DMA (and scatterlist) helpers are closely coupled
with the core device infrastructure and the device lifecycle, hence take
patches through the driver-core tree by default.

Cc: Abdiel Janulgue <abdiel.janulgue@gmail.com>
Link: https://lore.kernel.org/r/20250725202840.2251768-1-ojeda@kernel.org [1]
Acked-by: Abdiel Janulgue <abdiel.janulgue@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Danilo Krummrich

MAINTAINERS

@@ -7239,15 +7239,15 @@ F:	include/linux/swiotlb.h
 F:	kernel/dma/
 
 DMA MAPPING HELPERS DEVICE DRIVER API [RUST]
-M:	Abdiel Janulgue <abdiel.janulgue@gmail.com>
 M:	Danilo Krummrich <dakr@kernel.org>
+R:	Abdiel Janulgue <abdiel.janulgue@gmail.com>
 R:	Daniel Almeida <daniel.almeida@collabora.com>
 R:	Robin Murphy <robin.murphy@arm.com>
 R:	Andreas Hindborg <a.hindborg@kernel.org>
 L:	rust-for-linux@vger.kernel.org
 S:	Supported
 W:	https://rust-for-linux.com
-T:	git https://github.com/Rust-for-Linux/linux.git alloc-next
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git
 F:	rust/helpers/dma.c
 F:	rust/kernel/dma.rs
 F:	samples/rust/rust_dma.rs