Add assign/deassign PCI device hypercall APIs to assign a PCI device from SOS to
post-launched VM or deassign a PCI device from post-launched VM to SOS. This patch
is prepared for spliting passthrough PCI device from DM to HV.
The old assign/deassign ptdev APIs will be discarded.
Tracked-On: #4371
Signed-off-by: Li Fei1 <fei1.li@intel.com>