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>