genirq/msi: Provide struct msi_parent_ops

MSI parent domains must have some control over the MSI domains which are
built on top. On domain creation they need to fill in e.g. architecture
specific chip callbacks or msi domain ops to make the outermost domain
parent agnostic which is obviously required for architecture independence
etc.

The structure contains:

    1) A bitfield which exposes the supported functional features. This
       allows to check for features and is also used in the initialization
       callback to mask out unsupported features when the actual domain
       implementation requests a broader range, e.g. on x86 PCI multi-MSI
       is only supported by remapping domains but not by the underlying
       vector domain. The PCI/MSI code can then always request multi-MSI
       support, but the resulting feature set after creation might not
       have it set.

    2) An optional string prefix which is put in front of domain and chip
       names during creation of the MSI domain. That allows to keep the
       naming schemes e.g. on x86 where PCI-MSI domains have a IR- prefix
       when interrupt remapping is enabled.

    3) An initialization callback to sanity check the domain info of
       the to be created MSI domain, to restrict features and to
       apply changes in MSI ops and interrupt chip callbacks to
       accomodate to the particular MSI parent implementation and/or
       the underlying hierarchy.

Add a conveniance function to delegate the initialization from the
MSI parent domain to an underlying domain in the hierarchy.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221124232325.382485843@linutronix.de