ide_do_drive_cmd is called only with ide_preempt action argument. So
we can remove the action argument in ide_do_drive_cmd and ide_action_t
typedef.

This patch also includes two minor cleanups: 1) ide_do_drive_cmd
always succeeds so we don't need the return value; 2) the callers use
blk_rq_init before ide_do_drive_cmd so there is no need to initialize
rq->errors.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>