vfio: Use capability chains to handle device specific irq

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I401IF


CVE: NA

------------------------------

Caps the number of irqs with fixed indexes and uses capability chains
to chain device specific irqs.

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Kunkun <Jiang&lt;jiangkunkun@huawei.com>
[Eric: Put cap_offset at the end of the vfio_irq_info struct,
remove GFX IRQ at the moment and remove any reference to this latter
in the commit message]
Reviewed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>