cpufreq: dt: Don't use generic platdev driver for tango

On tango platforms, firmware configures the CPU clock, and Linux is
then only allowed to use the cpu_clk_divider to change the frequency.
Build the OPP table dynamically at init, in order to support whatever
firmware throws at us.

Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>