drm/i915: Execlists cannot pin a context without the object

Given that the intel_lr_context_pin cannot succeed without the object,
we cannot reach intel_lr_context_unpin() without first allocating that
object - so we can remove the redundant test.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1456485751-15213-1-git-send-email-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/intel_lrc.c

@@ -1145,10 +1145,6 @@ void intel_lr_context_unpin(struct intel_context *ctx,
 	struct drm_i915_gem_object *ctx_obj = ctx->engine[engine->id].state;
 
 	WARN_ON(!mutex_is_locked(&ctx->i915->dev->struct_mutex));
-
-	if (WARN_ON_ONCE(!ctx_obj))
-		return;
-
 	if (--ctx->engine[engine->id].pin_count == 0) {
 		kunmap(kmap_to_page(ctx->engine[engine->id].lrc_reg_state));
 		intel_unpin_ringbuffer_obj(ctx->engine[engine->id].ringbuf);