block: unalign call_single_data in struct request

A previous change blindly added massive alignment to the call_single_data structure in struct request. This ballooned it in size from 296 to 320 bytes on my setup, for no valid reason at all.

Use the unaligned struct __call_single_data variant instead.

---

index 100d0df38026..0ce8a372d506 100644
@@ -135,7 +135,7 @@ typedef __u32 __bitwise req_flags_t;
 struct request {
 	struct list_head queuelist;
 	union {
-		call_single_data_t csd;
+		struct __call_single_data csd;
 		u64 fifo_time;
 	};
 

Jens Axboe