clk: tegra: Fix constness for peripheral clocks

checkpatch now warns for const ** and expects const * const * to be used
instead. This means we have to update the prototypes and function
declarations to handle this change.

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Tested-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>