lkpi_pci_msi_desc_alloc() cached the descriptor, and with it the MSI
data, on first use. FreeBSD only programs the MSI message, and sets
cfg.msi.msi_data, once the first interrupt handler is set up. ath11k
calls irq_get_msi_desc() before request_irq() and again after it, in
ath11k_pci_config_msi_data(), to take the final data and hand it to
its firmware; it got the 0 cached by the first call.
Keep only the allocation, and refresh the data on every call.
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