block: Relocate BLK_MQ_CPU_WORK_BATCH

BLK_MQ_CPU_WORK_BATCH is defined in include/linux/blk-mq.h, but only used
in blk-mq.c, so relocate to block/blk-mq.h

Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20240719112912.3830443-6-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 260beea..3bd43b1 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -36,6 +36,8 @@ enum {
 	BLK_MQ_TAG_MAX		= BLK_MQ_NO_TAG - 1,
 };
 
+#define BLK_MQ_CPU_WORK_BATCH	(8)
+
 typedef unsigned int __bitwise blk_insert_t;
 #define BLK_MQ_INSERT_AT_HEAD		((__force blk_insert_t)0x01)