drm/i915/trace: i915_request.prio is a signed value

Don't confuse the poor developer by writing a negative value as a very
large positive, as the flow of requests is already complex enough.
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128151647.3820659-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_trace.h

@@ -800,7 +800,7 @@ TRACE_EVENT(i915_request_in,
 			     __field(u16, instance)
 			     __field(u32, seqno)
 			     __field(u32, port)
-			     __field(u32, prio)
+			     __field(s32, prio)
 			    ),
 
 	    TP_fast_assign(
@@ -813,7 +813,7 @@ TRACE_EVENT(i915_request_in,
 			   __entry->port = port;
 			   ),
 
-	    TP_printk("dev=%u, engine=%u:%u, ctx=%llu, seqno=%u, prio=%u, port=%u",
+	    TP_printk("dev=%u, engine=%u:%u, ctx=%llu, seqno=%u, prio=%d, port=%u",
 		      __entry->dev, __entry->class, __entry->instance,
 		      __entry->ctx, __entry->seqno,
 		      __entry->prio, __entry->port)