docs: Add documentation for SR-IOV and Virtualization Enhancements

docs: Add documentation for SR-IOV and Virtualization Enhancements

Documentation describes 5 new parameters being added regarding SR-IOV:
sriov_max_vfs
sriov_vq_flexible
sriov_vi_flexible
sriov_max_vi_per_vf
sriov_max_vq_per_vf

The description also includes the simplest possible QEMU invocation
and the series of NVMe commands required to enable SR-IOV support.

Signed-off-by: Lukasz Maniak <lukasz.maniak@linux.intel.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>