proportions: add @gfp to init functions

Percpu allocator now supports allocation mask.  Add @gfp to
[flex_]proportions init functions so that !GFP_KERNEL allocation masks
can be used with them too.

This patch doesn't make any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 91d73ef..5085994 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1777,7 +1777,7 @@
 	writeback_set_ratelimit();
 	register_cpu_notifier(&ratelimit_nb);
 
-	fprop_global_init(&writeout_completions);
+	fprop_global_init(&writeout_completions, GFP_KERNEL);
 }
 
 /**