qcom-cpufreq: Use new cpufreq_freq_transition_begin/end() API

Previous cpufreq_notify_transition() is deprecated in favor of
cpufreq_freq_transition_begin/end() API which provides serialization
guarantee for notifications.

Use the new API for transition notification.

Change-Id: I8d559e5c6ef4771986b24e017c900476da1f6cdf
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>