cpufreq: arm_big_little: Don't destroy/create freq table/clk for every cpu on/off

cpufreq: arm_big_little: Don't destroy/create freq table/clk for every cpu on/off

When a cpu goes down, exit would be called for it. Similarly for every cpu up
init would be called. This would result in same freq table and clk structure to
get freed/allocated again. There is no way for freq table/clk structures to
change between these calls.

Also, when we disable switcher, firstly cpufreq unregister would be called and
hence exit for all cpus and then register would be called, i.e. init would be
called.

For saving time/energy for both cases, lets not free table/clk until module exit
is not done.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>