main/busybox-initscripts: add ptp devices for VMs/Cloud instances

Add specifically-named PTP devices for Hyper-V/Azure, KVM, and VMware hypervisors. These can be used by Chrony for synchronising time more accurately with hypervisors than via NTP. As a VM/Cloud instance may have multiple "general" PTP devices (i.e. provided by some network cards) such as /dev/ptp0 and /dev/ptp1 these specifically named PTP devices are required to ensure that the correct PTP device is used by Chrony.