cpufreq: Save and restore min and max frequencies
In addition to restoring the previous governor after hotplug, restore
policy min and max frequencies.

CRs-fixed: 277482
Change-Id: I0d29281cecf4bd14ede06cd97d7bd3bffd0652c0
Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>