make blk-core.c:request_cachep static again

request_cachep needlessly became global.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Signed-off-by: NJens Axboe <axboe@carl.home.kernel.dk>

block/blk-core.c

@@ -38,7 +38,7 @@ static int __make_request(struct request_queue *q, struct bio *bio);
 /*
  * For the allocated request tables
  */
-struct kmem_cache *request_cachep;
+static struct kmem_cache *request_cachep;
 
 /*
  * For queue allocation