dmaengine: tegra: fix incorrect case of DMA

The use of Dma is annoying, since it is an acronym so should be all
upper case. Fix this throughout the driver.

Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>