ide-tape: use drive->pc_callback instead of pc->callback

The if-else block in the IRQ handler is only temporary so that bisect searches
don't break and it'll be removed after converting the remainder of the drivers.

There should be no functionality change resulting from this patch.

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