soc/tegra: pmc: Fix imbalanced clock disabling in error code path

The tegra_powergate_power_up() has a typo in the error code path where it
will try to disable clocks twice, fix it. In practice that error never
happens, so this is a minor correction.

Tested-by: Peter Geis <pgwipeout@gmail.com> # Ouya T30
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # PAZ00 T20 and TK1 T124
Tested-by: Matt Merhar <mattmerhar@protonmail.com> # Ouya T30
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>