dmaengine: add slave-dma maintainer

Slave-dma has become the predominant usage model for dmaengine and needs
special attention.  Memory-to-memory dma usage cases will continue to be
maintained by Dan.

Cc: Alan Cox <alan@linux.intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

MAINTAINERS

@@ -2124,6 +2124,7 @@ S:	Supported
 F:	fs/dlm/
 
 DMA GENERIC OFFLOAD ENGINE SUBSYSTEM
+M:	Vinod Koul <vinod.koul@intel.com>
 M:	Dan Williams <dan.j.williams@intel.com>
 S:	Supported
 F:	drivers/dma/