drm/i915: Use execlists_num_ports instead of size of array

There is function to tell how many ports we have, so use it.
We still have direct relationship with array size and port count,
so no harm was done.

Fixes: 76e70087 ("drm/i915: Make execlist port count variable")
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171010114857.13108-1-mika.kuoppala@intel.com

drivers/gpu/drm/i915/i915_guc_submission.c

@@ -500,7 +500,7 @@ static void i915_guc_submit(struct intel_engine_cs *engine)
 	const unsigned int engine_id = engine->id;
 	unsigned int n;
 
-	for (n = 0; n < ARRAY_SIZE(execlists->port); n++) {
+	for (n = 0; n < execlists_num_ports(execlists); n++) {
 		struct drm_i915_gem_request *rq;
 		unsigned int count;
 

drivers/gpu/drm/i915/intel_lrc.c

@@ -691,7 +691,7 @@ static void
 execlist_cancel_port_requests(struct intel_engine_execlists *execlists)
 {
 	struct execlist_port *port = execlists->port;
-	unsigned int num_ports = ARRAY_SIZE(execlists->port);
+	unsigned int num_ports = execlists_num_ports(execlists);
 
 	while (num_ports-- && port_isset(port)) {
 		struct drm_i915_gem_request *rq = port_request(port);