The Scalable IOV implementation will require notifying the VDCM driver when
an IRQ must be closed. This allows the VDCM to handle releasing stale IRQ
context values and properly reconfigure.

To handle this, introduce a new optional .irq_close callback to the VF
operations structure. This will be implemented by Scalable IOV to handle
the shutdown of the IRQ context.

Since the SR-IOV implementation does not need this, we must check that its
non-NULL before calling it.
Signed-off-by: NJacob Keller <jacob.e.keller@intel.com>
Tested-by: NMarek Szlosek <marek.szlosek@intel.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>