[BLOCK] Get rid of request_queue_t typedef

Some of the code has been gradually transitioned to using the proper
struct request_queue, but there's lots left. So do a full sweet of
the kernel and get rid of this typedef and replace its uses with
the proper type.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/block/xd.c b/drivers/block/xd.c
index 0d97b7e..624d30f 100644
--- a/drivers/block/xd.c
+++ b/drivers/block/xd.c
@@ -298,7 +298,7 @@
 }
 
 /* do_xd_request: handle an incoming request */
-static void do_xd_request (request_queue_t * q)
+static void do_xd_request (struct request_queue * q)
 {
 	struct request *req;