alpha: Streamline convoluted PCI error handling

miata_map_irq() handles PCI device and read config related errors in a
conditional block that is more complex than necessary.

Streamline the code flow and error handling.

No functional changes intended.

Link: https://lore.kernel.org/r/20230911125354.25501-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: ij-intel

arch/alpha/kernel/sys_miata.c

@@ -183,16 +183,17 @@ miata_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
            the 2nd 8259 controller. So we have to check for it first. */
 
 	if((slot == 7) && (PCI_FUNC(dev->devfn) == 3)) {
-		u8 irq=0;
 		struct pci_dev *pdev = pci_get_slot(dev->bus, dev->devfn & ~7);
-		if(pdev == NULL || pci_read_config_byte(pdev, 0x40,&irq) != PCIBIOS_SUCCESSFUL) {
-			pci_dev_put(pdev);
+		u8 irq = 0;
+		int ret;
+
+		if (!pdev)
 			return -1;
-		}
-		else	{
-			pci_dev_put(pdev);
-			return irq;
-		}
+
+		ret = pci_read_config_byte(pdev, 0x40, &irq);
+		pci_dev_put(pdev);
+
+		return ret == PCIBIOS_SUCCESSFUL ? irq : -1;
 	}
 
 	return COMMON_TABLE_LOOKUP;