drm/i915/perf: Drop lockdep assert for i915_oa_init_reg_state()

This is called from execlist context init which we need to be unlocked.
Commit f89823c21224 ("drm/i915/perf: Implement
I915_PERF_ADD/REMOVE_CONFIG interface") added a lockdep assert to this
path for unclear reasons, remove it again!

Fixes: f89823c21224 ("drm/i915/perf: Implement I915_PERF_ADD/REMOVE_CONFIG interface")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170810175743.25401-2-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

drivers/gpu/drm/i915/i915_perf.c

@@ -2173,8 +2173,6 @@ void i915_oa_init_reg_state(struct intel_engine_cs *engine,
 	struct drm_i915_private *dev_priv = engine->i915;
 	struct i915_perf_stream *stream = dev_priv->perf.oa.exclusive_stream;
 
-	lockdep_assert_held(&dev_priv->drm.struct_mutex);
-
 	if (engine->id != RCS)
 		return;