block: remove the unused blk_bounce enum

The enum has been replaced with the BLK_FEAT_BOUNCE_HIGH flag.

Reported-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20240619154623.450048-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

include/linux/blkdev.h

@@ -343,15 +343,6 @@ enum {
 	BLK_FLAGS_WRITE_CACHE_DISABLED		= (1u << 31),
 };
 
-/*
- * BLK_BOUNCE_NONE:	never bounce (default)
- * BLK_BOUNCE_HIGH:	bounce all highmem pages
- */
-enum blk_bounce {
-	BLK_BOUNCE_NONE,
-	BLK_BOUNCE_HIGH,
-};
-
 struct queue_limits {
 	unsigned int		features;
 	unsigned int		flags;