ide: remove ide_execute_pkt_cmd() (v2)

* Pass command structure to ide_execute_command() and skip
  __ide_set_handler() for ATAPI protocols on non-DRQ devices.

* Convert ide_issue_pc() to always use ide_execute_command()
  and remove no longer needed ide_execute_pkt_cmd().

v2:
* Fix for non-DRQ devices (based on report from Borislav).

There should be no functional changes caused by this patch.

Acked-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>