kern() instead and drop special
handling for REQ_TYPE_ATA_TASKFILE from ide_map_sg().

Note that REQ_RW setting is moved upwards as blk_rq_map_kern() uses it
to initialize bio rw flag.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Š¹ì