ide-pmac: use custom hwif->sg_max_nents only if DMA support is enabled

Move setting hwif->sg_max_nents from pmac_ide_setup_device()
to pmac_ide_setup_dma().
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: NSergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ppc/pmac.c

@@ -1133,8 +1133,6 @@ pmac_ide_setup_device(pmac_ide_hwif_t *pmif, ide_hwif_t *hwif, hw_regs_t *hw)
 		hwif->noprobe = 0;
 #endif /* CONFIG_PMAC_MEDIABAY */
 
-	hwif->sg_max_nents = MAX_DCMDS;
-
 #ifdef CONFIG_BLK_DEV_IDEDMA_PMAC
 	/* has a DBDMA controller channel */
 	if (pmif->dma_regs)
@@ -1751,6 +1749,8 @@ pmac_ide_setup_dma(pmac_ide_hwif_t *pmif, ide_hwif_t *hwif)
 		return;
 	}
 
+	hwif->sg_max_nents = MAX_DCMDS;
+
 	hwif->dma_host_set = &pmac_ide_dma_host_set;
 	hwif->dma_setup = &pmac_ide_dma_setup;
 	hwif->dma_exec_cmd = &pmac_ide_dma_exec_cmd;