vfio/pci: Consolidate irq cleanup on MSI/MSI-X disable

vfio_msi_disable() releases all previously allocated state
associated with each interrupt before disabling MSI/MSI-X.

vfio_msi_disable() iterates twice over the interrupt state:
first directly with a for loop to do virqfd cleanup, followed
by another for loop within vfio_msi_set_block() that removes
the interrupt handler and its associated state using
vfio_msi_set_vector_signal().

Simplify interrupt cleanup by iterating over allocated interrupts
once.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/837acb8cbe86a258a50da05e56a1f17c1a19abbe.1683740667.git.reinette.chatre@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>