cs5530: 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.

Also this host driver requires valid PCI BAR4 for normal operation so
check it in ->init_chipset and fail initialization if not set.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/pci/cs5530.c

 /*
- * linux/drivers/ide/pci/cs5530.c		Version 0.73	Mar 10 2007
+ * linux/drivers/ide/pci/cs5530.c		Version 0.74	Jul 28 2007
  *
  * Copyright (C) 2000			Andre Hedrick <andre@linux-ide.org>
  * Copyright (C) 2000			Mark Lord <mlord@pobox.com>
@@ -207,6 +207,9 @@ static unsigned int __devinit init_chipset_cs5530 (struct pci_dev *dev, const ch
 	struct pci_dev *master_0 = NULL, *cs5530_0 = NULL;
 	unsigned long flags;
 
+	if (pci_resource_start(dev, 4) == 0)
+		return -EFAULT;
+
 	dev = NULL;
 	while ((dev = pci_get_device(PCI_VENDOR_ID_CYRIX, PCI_ANY_ID, dev)) != NULL) {
 		switch (dev->device) {
@@ -325,6 +328,9 @@ static void __devinit init_hwif_cs5530 (ide_hwif_t *hwif)
 			/* needs autotuning later */
 	}
 
+	if (hwif->dma_base == 0)
+		return;
+
 	hwif->atapi_dma = 1;
 	hwif->ultra_mask = 0x07;
 	hwif->mwdma_mask = 0x07;