clocksource/drivers/tegra: Drop unneeded typecasting in one place

There is no need to cast void because kernel allows to do that without
a warning message from a compiler.

Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>