maintainers: add dma engine tree details

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

MAINTAINERS

@@ -2169,6 +2169,8 @@ M:	Dan Williams <dan.j.williams@intel.com>
 S:	Supported
 F:	drivers/dma/
 F:	include/linux/dma*
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx.git
+T:	git git://git.infradead.org/users/vkoul/slave-dma.git (slave-dma)
 
 DME1737 HARDWARE MONITOR DRIVER
 M:	Juerg Haefliger <juergh@gmail.com>