clocksource/drivers/tegra: Set up maximum-ticks limit properly

Tegra's timer has 29 bits for the counter and for the "load" register
which sets counter to a load-value. The counter's value is lower than
the actual value by 1 because it starts to decrement after one tick,
hence the maximum number of ticks that hardware can handle equals to
29 bits + 1.

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