block: initialize the target bio in __bio_clone_fast

block: initialize the target bio in __bio_clone_fast

All callers of __bio_clone_fast initialize the bio first.  Move that
initialization into __bio_clone_fast instead.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Mike Snitzer <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>