vfio/qat: Add vfio_pci driver for Intel QAT SR-IOV VF devices

Add vfio pci variant driver for Intel QAT SR-IOV VF devices. This driver
registers to the vfio subsystem through the interfaces exposed by the
subsystem. It follows the live migration protocol v2 defined in
uapi/linux/vfio.h and interacts with Intel QAT PF driver through a set
of interfaces defined in qat/qat_mig_dev.h to support live migration of
Intel QAT VF devices.

This version only covers migration for Intel QAT GEN4 VF devices.

Co-developed-by: Yahui Cao <yahui.cao@intel.com>
Signed-off-by: Yahui Cao <yahui.cao@intel.com>
Signed-off-by: Xin Zeng <xin.zeng@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240426064051.2859652-1-xin.zeng@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>