clk: tegra: Add the DFLL as a possible parent of the cclk_g clock

The DFLL clocksource was missing from the list of possible parents for
the fast CPU cluster. Add it to the list.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Signed-off-by: Mikko Perttunen <mikko.perttunen@kapsi.fi>
Acked-by: Michael Turquette <mturquette@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>