Revert "PCI/MSI: Unmap MSI-X region on error"

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

Revert "PCI/MSI: Unmap MSI-X region on error"

This reverts commit 1a8d4c6ecb4c81261bcdf13556abd4a958eca202.

Commit 1a8d4c6ecb4c ("PCI/MSI: Unmap MSI-X region on error") added an
iounmap(dev->msix_base) on the error path of msix_capability_init() to
release the MSI-X region when msix_setup_interrupts() fails.

When msix_setup_interrupts() fails, the call chain is:

msix_setup_interrupts()
-> __msix_setup_interrupts()
struct pci_dev *dev __free(free_msi_irqs) = __dev;
...
return ret; // __free cleanup fires on error

The __free(free_msi_irqs) cleanup calls pci_free_msi_irqs(), which
already handles the unmap:

void pci_free_msi_irqs(struct pci_dev *dev)
{
pci_msi_teardown_msi_irqs(dev);
if (dev->msix_base) {
iounmap(dev->msix_base); // already unmapped here
dev->msix_base = NULL; // and set to NULL
}
}

So dev->msix_base is unmapped and set to NULL before
msix_setup_interrupts() returns to msix_capability_init(). The
"goto out_unmap" introduced by commit 1a8d4c6ecb4c ("PCI/MSI: Unmap
MSI-X region on error") then calls iounmap() a second time on a NULL
pointer.

This was reproduced on Intel Emerald Rapids (192 CPUs) while
running tools/testing/selftests/kexec/test_kexec_jump.sh:

WARNING: CPU#44 at iounmap+0x2a/0xe0
RIP: 0010:iounmap+0x2a/0xe0
RDI: 0000000000000000
Call Trace:
msix_capability_init+0x317/0x3f0
__pci_enable_msix_range+0x21d/0x2c0
pci_alloc_irq_vectors_affinity+0xa9/0x130
nvme_setup_io_queues+0x2a8/0x420 [nvme]
nvme_reset_work+0x151/0x340 [nvme]
...

RDI=0 confirms iounmap() is called with NULL.

Restore the original "goto out_disable" and leave the unmap to the
existing __free(free_msi_irqs) cleanup.