Factor out waiting for good ireason from idetape_transfer_pc()
to ide_tape_wait_ireason() as a preparation for adding generic
ide_transfer_pc() helper.

There should be no functional changes caused by this patch.

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