agp/ati: Use PCI_COMMAND instead of hard-coded 4

We're accessing the PCI_COMMAND register here, so use the appropriate
#define.  The bit we're writing (1 << 14) isn't defined by the PCI or PCIe
spec, so we don't have a name for it.

No functional change.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

drivers/char/agp/ati-agp.c

@@ -221,8 +221,8 @@ static int ati_configure(void)
 	readl(ati_generic_private.registers+ATI_GART_FEATURE_ID);	/* PCI Posting.*/
 
 	/* SIGNALED_SYSTEM_ERROR @ NB_STATUS */
-	pci_read_config_dword(agp_bridge->dev, 4, &temp);
-	pci_write_config_dword(agp_bridge->dev, 4, temp | (1<<14));
+	pci_read_config_dword(agp_bridge->dev, PCI_COMMAND, &temp);
+	pci_write_config_dword(agp_bridge->dev, PCI_COMMAND, temp | (1<<14));
 
 	/* Write out the address of the gatt table */
 	writel(agp_bridge->gatt_bus_addr, ati_generic_private.registers+ATI_GART_BASE);