drm/i915: Wrap engine->context_pin() and engine->context_unpin()

Make life easier in upcoming patches by moving the context_pin and
context_unpin vfuncs into inline helpers.

v2: Fixup mock_engine to mark the context as pinned on use.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180430131503.5375-2-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6b0c67a..4090bfd 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3234,7 +3234,7 @@ void i915_gem_reset(struct drm_i915_private *dev_priv,
 				      stalled_mask & ENGINE_MASK(id));
 		ctx = fetch_and_zero(&engine->last_retired_context);
 		if (ctx)
-			engine->context_unpin(engine, ctx);
+			intel_context_unpin(ctx, engine);
 
 		/*
 		 * Ostensibily, we always want a context loaded for powersaving,
@@ -5291,7 +5291,7 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
 	for_each_engine(engine, i915, id) {
 		struct i915_vma *state;
 
-		state = ctx->engine[id].state;
+		state = to_intel_context(ctx, engine)->state;
 		if (!state)
 			continue;