Virtio SPI Linux driver

Merge series from Haixu Cui <quic_haixcui@quicinc.com>:

This is the 10th version of the virtio SPI Linux driver patch series which is
intended to be compliant with the upcoming virtio specification
version 1.4. The specification can be found in repository:
https://github.com/oasis-tcs/virtio-spec.git branch virtio-1.4.