cpufreq: qcom-hw: Reset cancel_throttle when policy is re-enabled

If LMH (Limits Management Hardware) is available, when a policy is
disabled by unplugging the last online CPU of policy->cpus,
qcom_cpufreq_hw_cpu_offline() sets cancel_throttle=true.
cancel_throttle is not reset when the policy is re-enabled with any
of the CPU in policy->cpus being plugged in. So reset it.

This patch also adds an early exit check.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>