cpufreq: msm: remove gov_mutex from stop

The stop could end up calling set_frequency callback. The set_frequency
callback takes the same gov_mutex lock and we end up in a deadlock.

Fix this by removing the locks around stop.

Change-Id: Ic687d92825f253aa3e23e4bcaf3c96d5879d4b43
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>