dma-mapping: update MAINTAINERS

Marek has graciously offered to maintain the dma-mapping tree.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Christoph Hellwig

MAINTAINERS

@@ -6878,7 +6878,6 @@ F:	kernel/dma/map_benchmark.c
 F:	tools/testing/selftests/dma/
 
 DMA MAPPING HELPERS
-M:	Christoph Hellwig <hch@lst.de>
 M:	Marek Szyprowski <m.szyprowski@samsung.com>
 R:	Robin Murphy <robin.murphy@arm.com>
 L:	iommu@lists.linux.dev