vfio/ccw: vfio based subchannel passthrough driver

vfio/ccw: vfio based subchannel passthrough driver

We use the IOMMU_TYPE1 of VFIO to realize the subchannels
passthrough, implement a vfio based subchannels passthrough
driver called "vfio-ccw".

Support qemu parameters in the style of:
"-device vfio-ccw,sysfsdev=$mdev_file_path,devno=xx.x.xxxx'

Reviewed-by: Eric Auger <[email protected]>
Acked-by: Alex Williamson <[email protected]>
Signed-off-by: Xiao Feng Ren <[email protected]>
Signed-off-by: Dong Jia Shi <[email protected]>
Message-Id: <20170517004813[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>