PCI/MSI: Prevent MSI hardware interrupt number truncation

[Brad Figg]

    While calculating the hardware interrupt number for a MSI interrupt, the
    higher bits (i.e. from bit-5 onwards a.k.a domain_nr >= 32) of the PCI
    domain number gets truncated because of the shifted value casting to return
    type of pci_domain_nr() which is 'int'. This for example is resulting in
    same hardware interrupt number for devices 0019:00:00.0 and 0039:00:00.0.

    To address this cast the PCI domain number to 'irq_hw_number_t' before left
    shifting it to calculate the hardware interrupt number.

    Please note that this fixes the issue only on 64-bit systems and doesn't
    change the behavior for 32-bit systems i.e. the 32-bit systems continue to
    have the issue. Since the issue surfaces only if there are too many PCIe
    controllers in the system which usually is the case in modern server
    systems and they don't tend to run 32-bit kernels.