dmaengine/MAINTAINERS: Add Andy as Co-Maintainer of DW DMA Controller

Andy has done enough work on Synopsys Designware DMA Controller and I believe he
should Co-Maintain this driver along with me. So this patch.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>