iommu: Fix pirq conflict issue when guest adopts per-cpu vector.

iommu: Fix pirq conflict issue when guest adopts per-cpu vector.

Latest Linux and Windows may adopt per-cpu vector instead of global
vector, so same vector in different vcpu may correspond to different
interrupt sources. That is to say, vector and pirq should be 1:n
mapping, and the array msi_gvec_pirq can't meet the mapping
requirement, so need to improve the related logic, otherwise it may
introduce strange issues.

Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>