clk: tegra: Do not disable PLLE when under hardware control

Software should not disable PLLE if PLLE is already put under hardware
control.

Signed-off-by: Mark Kuo <mkuo@nvidia.com>
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>