clk: tegra: Add the APB2APE audio clock on Tegra210

The APB2APE clock for the audio subsystem is required for powering up the
audio power domain and accessing the various modules in this subsystem on
Tegra210 devices. Add this clock for Tegra210.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>