ARM: tegra: dma: not required to move requestor when stopping.

It is not require to move the requestor of dma to INVALID
option before stopping dma.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>