drm/i915/selftests: cond_resched() within the longer buddy tests

Let the scheduler have a breather in between passes of the longer buddy
tests. Important if we are running under kasan etc and this takes far
longer than usual!
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190829170848.969-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/selftests/i915_buddy.c

@@ -375,6 +375,8 @@ static int igt_buddy_alloc_smoke(void *arg)
 
 		if (err)
 			break;
+
+		cond_resched();
 	}
 
 	if (err == -ENOMEM)
@@ -687,6 +689,8 @@ static int igt_buddy_alloc_range(void *arg)
 		rem -= size;
 		if (!rem)
 			break;
+
+		cond_resched();
 	}
 
 	if (err == -ENOMEM)