drm/amdgpu/powerplay: fix locking typo

Fixes: 2a507105 ("drm/amd/powerplay: add global PowerPlay mutex.")
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/amd_powerplay.c

@@ -894,7 +894,7 @@ static int pp_dpm_set_sclk_od(void *handle, uint32_t value)
 
 	mutex_lock(&pp_handle->pp_lock);
 	ret = hwmgr->hwmgr_func->set_sclk_od(hwmgr, value);
-	mutex_lock(&pp_handle->pp_lock);
+	mutex_unlock(&pp_handle->pp_lock);
 	return ret;
 }