arm/tegra: don't export clk_measure_input_freq

don't export clk_measure_input_freq as its functionality is also available
using clk_get_rate().

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Olof Johansson <olof@lixom.net>