block: Remove request.write_hint

Commit c75e707fe1 ("block: remove the per-bio/request write hint")
removed all code that uses the struct request write_hint member. Hence
also remove 'write_hint' itself.

Reviewed-by: Ming Lei <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Keith Busch <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

include/linux/blk-mq.h

@@ -140,7 +140,6 @@ struct request {
 	struct blk_crypto_keyslot *crypt_keyslot;
 #endif
 
-	unsigned short write_hint;
 	unsigned short ioprio;
 
 	enum mq_rq_state state;