ARM: tegra: add sysfs support for tegra cpuquiet driver

Change-Id: I215c5de8e98d139a93113978e1e27adb5a6b252c
Signed-off-by: Sai Charan Gurrappadi <sgurrappadi@nvidia.com>
Reviewed-on: http://git-master/r/111283
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>