MAINTAINERS: dmaengine: fix the header file for dmaengine

The headers were listed as include/linux/dma* which is wrong as we have
other files in include/linux/dma* which have nothing to do with dmaengine so
update it to include/linux/dmaengine.h

Signed-off-by: Vinod Koul <vinod.koul@intel.com>

MAINTAINERS

@@ -3182,7 +3182,7 @@ L:	dmaengine@vger.kernel.org
 Q:	https://patchwork.kernel.org/project/linux-dmaengine/list/
 S:	Maintained
 F:	drivers/dma/
-F:	include/linux/dma*
+F:	include/linux/dmaengine.h
 F:	Documentation/dmaengine/
 T:	git git://git.infradead.org/users/vkoul/slave-dma.git