"S5" is one of the ACPI sleep states which means the function to shut
down the VMs.
On ACRN, the User VM must be shut down before powering off the Service
VM, so we need a vUART channel to communicate between the Service VM
and User VMs.
This patch adds a vUART channel for each User VM connect to Service VM
Tracked-On: #8782
Signed-off-by: Chenli Wei <chenli.wei@intel.com>
Reviewed-by: Junjie Mao <junjie.mao@intel.com>
