Revert "PCI/MSI: Provide pci_ims_alloc/free_irq()"

This reverts commit c9e5bea2.

IMS (Interrupt Message Store) support appeared in v6.2, but there are no
users yet.

Remove it for now.  We can add it back when a user comes along.  If this is
re-added later, the relevant part of 41efa431 ("PCI/MSI: Provide stubs
for IMS functions") should be squashed into it.

Link: https://lore.kernel.org/r/20240410221307.2162676-3-helgaas@kernel.org


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>