triflex: add missing ->dma_base check

If ->dma_base is not set (== PCI BAR4 cannot be reserved) then DMA hooks
shouldn't be initialized or bad things will happen.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/pci/triflex.c

@@ -115,6 +115,9 @@ static void __devinit init_hwif_triflex(ide_hwif_t *hwif)
 	hwif->tuneproc = &triflex_tune_drive;
 	hwif->speedproc = &triflex_tune_chipset;
 
+	if (hwif->dma_base == 0)
+		return;
+
 	hwif->atapi_dma  = 1;
 	hwif->mwdma_mask = 0x07;
 	hwif->swdma_mask = 0x07;