Cpufreq: create/remove percpu sysfs nodes once

On cpu hotplug on/off, percpu "cpufreq" sysfs node and it's
sub nodes are freshly created and removed. This increases
cpu up/down latency.

Create percpu "cpufreq" sysfs node and it's sub nodes in driver
registration and remove it in unregistration. This decreases
cpu up/down latency significantly.

Signed-off-by: Puneet Saxena <puneets@nvidia.com>
Reviewed-on: http://git-master/r/146812
(cherry picked from commit 298382285677fa791098d117ccc0a0a3d9ab0f9a)
Reviewed-on: http://git-master/r/219379
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Sachin Nikam <snikam@nvidia.com>

modified for use on Mako by faux123

Change-Id: I2dba380f0475643f57cb2924f949e7a728cb0b26