cpufreq: conservative: update frequency when limits are relaxed

Reevaluate CPU load and update frequency immediately whenever limits
are changed. Currently conservative doesn't do that when limits are
relaxed, wasting power on systems with relatively low sampling rate.

Change-Id: I271d36b9c61b2746b035ca5b6214e699c8034d42
Signed-off-by: Michal Pecio <mpecio@nvidia.com>
Reviewed-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
(cherry picked from commit ad1c3a2f43acd7e26881bd941e77a6fb0535f6a9)