drm/i915: Use HWS for seqno tracking everywhere

By using the same address for storing the HWS on every platform, we can
remove the platform specific vfuncs and reduce the get-seqno routine to
a single read of a cached memory location.

v2: Fix semaphore_passed() to look at the signaling engine (not the
waiter's)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467390209-3576-8-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index a3bbf2d..7cdb02d 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -146,7 +146,7 @@
 	first = true;
 	parent = NULL;
 	completed = NULL;
-	seqno = engine->get_seqno(engine);
+	seqno = intel_engine_get_seqno(engine);
 
 	 /* If the request completed before we managed to grab the spinlock,
 	  * return now before adding ourselves to the rbtree. We let the
@@ -296,7 +296,7 @@
 			 * the first_waiter. This is undesirable if that
 			 * waiter is a high priority task.
 			 */
-			u32 seqno = engine->get_seqno(engine);
+			u32 seqno = intel_engine_get_seqno(engine);
 
 			while (i915_seqno_passed(seqno, to_wait(next)->seqno)) {
 				struct rb_node *n = rb_next(next);