drm/i915: Drop assertion that ce->pin_mutex guards state updates

The actual conditions are that we know the GPU is not accessing the
context, and we hold a pin on the context image to allow CPU access. We
used a fake lock on ce->pin_mutex so that we could try and use lockdep
to assert that access is serialised, but the various different
hardirq/softirq contexts where we need to *fake* holding the pin_mutex
are causing more trouble.

Still it would be nice if we did have a way to reassure ourselves that
the direct update to the context image is serialised with GPU execution.
In the meantime, stop lockdep complaining about false irq inversions.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111923
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191022122845.25038-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_perf.c

@@ -2615,7 +2615,6 @@ void i915_oa_init_reg_state(const struct intel_context *ce,
 	struct i915_perf_stream *stream;
 
 	/* perf.exclusive_stream serialised by gen8_configure_all_contexts() */
-	lockdep_assert_held(&ce->pin_mutex);
 
 	if (engine->class != RENDER_CLASS)
 		return;