Revert "PCI/MSI: Provide IMS (Interrupt Message Store) support"

This reverts commit 0194425a.

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/20240410221307.2162676-4-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>