cpufreq: arm_big_little: use generic OPP functions for {init, free}_opp_table

Currently when performing random CPU hot-plugs and suspend-to-ram(S2R)
on systems using arm_big_little cpufreq driver, we get warnings similar
to something like below:

cpu cpu1: _opp_add: duplicate OPPs detected. Existing: freq: 600000000,
	volt: 800000, enabled: 1. New: freq: 600000000, volt: 800000, enabled: 1

This is mainly because the OPPs for the shared cpus are not set. We can
just use dev_pm_opp_of_cpumask_add_table in case the OPPs are obtained
from DT(arm_big_little_dt.c) or use dev_pm_opp_set_sharing_cpus if the
OPPs are obtained by other means like firmware(e.g. scpi-cpufreq.c)

Also now that the generic dev_pm_opp{,_of}_cpumask_remove_table can
handle removal of opp table and entries for all associated CPUs, we can
re-use dev_pm_opp{,_of}_cpumask_remove_table as free_opp_table in
cpufreq_arm_bL_ops.

This patch makes necessary changes to reuse the generic OPP functions for
{init,free}_opp_table and thereby eliminating the warnings.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>