powerpc/xive: fix kmemleak caused by incorrect chip_data lookup

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

powerpc/xive: fix kmemleak caused by incorrect chip_data lookup

The kmemleak reports the following memory leak:

Unreferenced object 0xc0000002a7fbc640 (size 64):
comm "kworker/8:1", pid 540, jiffies 4294937872
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 00 00 09 04 00 04 00 00 ................
00 00 a7 81 00 00 0a c0 00 00 08 04 00 04 00 00 ................
backtrace (crc 177d48f6):
__kmalloc_cache_noprof+0x520/0x730
xive_irq_alloc_data.constprop.0+0x40/0xe0
xive_irq_domain_alloc+0xd0/0x1b0
irq_domain_alloc_irqs_parent+0x44/0x6c
pseries_irq_domain_alloc+0x1cc/0x354
irq_domain_alloc_irqs_parent+0x44/0x6c
msi_domain_alloc+0xb0/0x220
irq_domain_alloc_irqs_locked+0x138/0x4d0
__irq_domain_alloc_irqs+0x8c/0xfc
__msi_domain_alloc_irqs+0x214/0x4d8
msi_domain_alloc_irqs_all_locked+0x70/0xf8
pci_msi_setup_msi_irqs+0x60/0x78
__pci_enable_msix_range+0x54c/0x98c
pci_alloc_irq_vectors_affinity+0x16c/0x1d4
nvme_pci_enable+0xac/0x9c0 [nvme]
nvme_probe+0x340/0x764 [nvme]

This occurs when allocating MSI-X vectors for an NVMe device. During
allocation the XIVE code creates a struct xive_irq_data and stores it
in irq_data->chip_data.

When the MSI-X irqdomain is later freed, xive_irq_free_data() is
responsible for retrieving this structure and freeing it. However,
after commit cc0cc23babc9 ("powerpc/xive: Untangle xive from child
interrupt controller drivers"), xive_irq_free_data() retrieves the
chip_data using irq_get_chip_data(), which looks up the data through
the child domain.

This is incorrect because the XIVE-specific irq data is associated with
the XIVE (parent) domain. As a result the lookup fails and the allocated
struct xive_irq_data is never freed, leading to the kmemleak report
shown above.

Fix this by retrieving the irq_data from the correct domain using
irq_domain_get_irq_data() and then accessing the chip_data via
irq_data_get_irq_chip_data().