am53c974: Fix crash during modprobe

On systems with shared interrupts the interrupt routine might
be called as soon as the interrupt is enabled.
As this might happen before pci_set_drvdata() is called the
system would crash.

Reported-by: Andreas Brogle <[e-mail]>
Tested-by: Andreas Brogle <[e-mail]>
Signed-off-by: Hannes Reinecke <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/am53c974.c

···
 		goto fail_unmap_regs;
 	}
 
+	pci_set_drvdata(pdev, pep);
+
 	err = request_irq(pdev->irq, scsi_esp_intr, IRQF_SHARED,
 			  DRV_MODULE_NAME, esp);
 	if (err < 0) {
···
 	/* Assume 40MHz clock */
 	esp->cfreq = 40000000;
 
-	pci_set_drvdata(pdev, pep);
-
 	err = scsi_esp_register(esp, &pdev->dev);
 	if (err)
 		goto fail_free_irq;
···
 fail_free_irq:
 	free_irq(pdev->irq, esp);
 fail_unmap_command_block:
+	pci_set_drvdata(pdev, NULL);
 	pci_free_consistent(pdev, 16, esp->command_block,
 			    esp->command_block_dma);
 fail_unmap_regs:
···
 
 	scsi_esp_unregister(esp);
 	free_irq(pdev->irq, esp);
+	pci_set_drvdata(pdev, NULL);
 	pci_free_consistent(pdev, 16, esp->command_block,
 			    esp->command_block_dma);
 	pci_iounmap(pdev, esp->regs);