cpufreq: brcmstb-avs-cpufreq: remove development debug support

This debug code was helpful while developing the driver, but it isn't
being used for anything anymore.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>