drm/i915: Make LRC (un)pinning work on context and engine

Previously intel_lr_context_(un)pin were operating on requests
which is in conflict with their names.

If we make them take a context and an engine, it makes the names
make more sense and it also makes future fixes possible.

v2: Rebase for default_context/kernel_context change.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Nick Hoath <nicholas.hoath@intel.com>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c1bb6a6..a928823 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2680,7 +2680,7 @@
 
 	if (ctx) {
 		if (i915.enable_execlists && ctx != req->i915->kernel_context)
-			intel_lr_context_unpin(req);
+			intel_lr_context_unpin(ctx, req->ring);
 
 		i915_gem_context_unreference(ctx);
 	}