MAINTAINERS: Update Tegra DMA maintainers

Update the Tegra DMA driver maintainer field to include the newly added
Tegra210 ADMA and add Jon Hunter as a co-maintainer for Tegra DMA.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>