memory: tegra: Do not handle error from wait_for_completion_timeout()

Contrary to its wait_for_completion_timeout_interruptible() sibling, the
wait_for_completion_timeout() function does not return an error.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>