clk: tegra: Unlock top rates for Tegra124 DFLL clock

The new determine_rate prototype allows for clock rates exceeding
2^31-1 Hz to be used. Switch the DFLL clock to use determine_rate
instead of round_rate and unlock the top rates supported by the
Tegra124.

Signed-off-by: Mikko Perttunen <mikko.perttunen@kapsi.fi>
Signed-off-by: Thierry Reding <treding@nvidia.com>