A set of updates for the interrupt susbsystem:
- Prevent possible NULL pointer derefences in irq_data_get_affinity_mask()
and irq_domain_create_hierarchy().
- Take the per device MSI lock before invoking code which relies
on it being hold.
- Make sure that MSI descriptors are unreferenced before freeing
them. This was overlooked when the platform MSI code was converted to
use core infrastructure and results in a fals positive warning.
- Remove dead code in the MSI subsystem.
- Clarify the documentation for pci_msix_free_irq().
- More kobj_type constification.