bsg-lib: initialize the bsg_job in bsg_transport_sg_io_fn

Directly initialize the bsg_job structure instead of relying on the
->.initialize_rq_fn indirection.  This also removes the superflous
initialization of the second request used for BIDI requests.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20211021060607.264371-5-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>