v3d: Fix return value from fence_finish.

We needed to convert from a -errno to a boolean success value.  Fixes:

GTF-GLES3.gtf.GL3Tests.sync.sync_functionality_clientwaitsync_flush
GTF-GLES3.gtf.GL3Tests.sync.sync_functionality_clientwaitsync_signaled

src/gallium/drivers/v3d/v3d_fence.c

@@ -70,7 +70,7 @@ v3d_fence_finish(struct pipe_screen *pscreen,
         struct v3d_screen *screen = v3d_screen(pscreen);
         struct v3d_fence *f = (struct v3d_fence *)pf;
 
-        return drmSyncobjWait(screen->fd, &f->sync, 1, timeout_ns, 0, NULL);
+        return drmSyncobjWait(screen->fd, &f->sync, 1, timeout_ns, 0, NULL) == 0;
 }
 
 struct v3d_fence *