Revert "genirq/msi: Provide constants for PCI/IMS support"

This reverts commit e23d4192.

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.

Link: https://lore.kernel.org/r/20240410221307.2162676-8-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>