scsi: lpfc: Fix ioremap issues in lpfc_sli4_pci_mem_setup()

In the Linux kernel, the following vulnerability has been resolved:

scsi: lpfc: Fix ioremap issues in lpfc_sli4_pci_mem_setup()

When if_type equals zero and pci_resource_start(pdev, PCI_64BIT_BAR4)
returns false, drbl_regs_memmap_p is not remapped. This passes a NULL
pointer to iounmap(), which can trigger a WARN() on certain arches.

When if_type equals six and pci_resource_start(pdev, PCI_64BIT_BAR4)
returns true, drbl_regs_memmap_p may has been remapped and
ctrl_regs_memmap_p is not remapped. This is a resource leak and passes a
NULL pointer to iounmap().

To fix these issues, we need to add null checks before iounmap(), and
change some goto labels.