drm/msm/adreno: Call dev_pm_opp_put()

We need to call dev_pm_opp_put() to put back the reference
for the OPP struct after calling the various dev_pm_opp_get_*
functions.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>