cpufreq: use kzalloc() to allocate memory for cpufreq_frequency_table

Few drivers are using kmalloc() to allocate memory for frequency
tables and since we will have an additional field '.flags' in
'struct cpufreq_frequency_table', these might become unstable.
Better get these fixed by replacing kmalloc() by kzalloc() instead.

Along with that we also remove use of .driver_data from SPEAr driver
as it doesn't use it at all. Also, writing zero to .driver_data is not
required for powernow-k8 as it is already zero.

Reported-and-reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>