block: remove the NULL ioc check in put_io_context

No caller passes in a NULL pointer, so remove the check.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211209063131.18537-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-ioc.c

@@ -155,9 +155,6 @@ void put_io_context(struct io_context *ioc)
 	unsigned long flags;
 	bool free_ioc = false;
 
-	if (ioc == NULL)
-		return;
-
 	BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
 
 	/*