cpufreq: Export user_policy min/max

Add sysfs nodes for user_policy min and max settings.

Bug 888312

Change-Id: Ife8ec07f8faebc0c04e7ecf6e24976a311bad73b
Reviewed-on: http://git-master/r/72201
Signed-off-by: Antti P Miettinen <amiettinen@nvidia.com>
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Reviewed-on: http://git-master/r/75882
Reviewed-by: Automatic_Commit_Validation_User

Rebase-Id: Rf145967a22a5d871d01bb1334a2e7d366a6612fd

Conflicts:
	drivers/cpufreq/cpufreq.c

Conflicts:
	drivers/cpufreq/cpufreq.c