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/backing-dev.c b/mm/backing-dev.c
index f19a818..64ec49d 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -470,7 +470,7 @@
 	bdi->write_bandwidth = INIT_BW;
 	bdi->avg_write_bandwidth = INIT_BW;
 
-	err = fprop_local_init_percpu(&bdi->completions);
+	err = fprop_local_init_percpu(&bdi->completions, GFP_KERNEL);
 
 	if (err) {
 err: