macio: fix NULL pointer dereference when issuing IDE trim

Commit ef0e64a9 "ide: pass IDEState to trim AIO callback" changed the
IDE trim callback from using a BlockBackend to an IDEState but forgot to update
the dma_blk_io() call in hw/ide/macio.c accordingly.

Without this fix qemu-system-ppc segfaults when issuing an IDE trim command on
any of the PPC Mac machines (easily triggered by running the Debian installer).
Reported-by: NHoward Spoelstra <hsp.cat7@gmail.com>
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: NAnton Nefedov <anton.nefedov@virtuozzo.com>
Message-id: 20180223184700.28854-1-mark.cave-ayland@ilande.co.uk
Signed-off-by: NJohn Snow <jsnow@redhat.com>

hw/ide/macio.c

@@ -187,7 +187,7 @@ static void pmac_ide_transfer_cb(void *opaque, int ret)
         break;
     case IDE_DMA_TRIM:
         s->bus->dma->aiocb = dma_blk_io(blk_get_aio_context(s->blk), &s->sg,
-                                        offset, 0x1, ide_issue_trim, s->blk,
+                                        offset, 0x1, ide_issue_trim, s,
                                         pmac_ide_transfer_cb, io,
                                         DMA_DIRECTION_TO_DEVICE);
         break;