Revert "block: Clear kernel memory before copying to user"

BugLink: https://bugs.launchpad.net/bugs/1837235

This reverts commit aceb27a7 as
it seems to be part of a set causing regressions on 32bit.
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

block/bio.c

@@ -1238,7 +1238,6 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
 		if (ret)
 			goto cleanup;
 	} else {
-		zero_fill_bio(bio);
 		iov_iter_advance(iter, bio->bi_iter.bi_size);
 	}