dmaengine: tegra210-adma: Don't program FIFO threshold

The Tegra210 ADMA supports two modes for transferring data to a FIFO
which are ...

1. Transfer data to/from the FIFO as soon as a single burst can be
   transferred.
2. Transfer data to/from the FIFO based upon FIFO thresholds, where
   the FIFO threshold is specified in terms on multiple bursts.

Currently, the ADMA driver programs the FIFO threshold values in the
FIFO_CTRL register, but never enables the transfer mode that uses
these threshold values. Given that these have never been used so far,
simplify the ADMA driver by removing the programming of these threshold
values.

Signed-off-by: Jonathan Hunter <jonathanh@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20190731101639.22755-1-jonathanh@nvidia.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>