Several posts (e.g., viewtopic.php?f=18&t=4675, viewtopic.php?f=28&t=4996) describe problems with netcfg not starting a DHCP Ethernet interface at boot. I had the same problem. It also occurs when a static IP address is assigned and the cable is not plugged in a when the system is booted.
The root cause of these problems is that ArchLinuxARM-armv5te-latest is missing the ifplugd package. ifplugd will bring up the network interface when the link state changes to up -- there is no need to insert artificial delays (PRE_UP="sleep x") or a systemd workaround service (ifconfig up; ifconfig down; ifconfig up; dhcpcd).
The next time ArchLinuxARM-armv5te-latest is prepared, it needs to have the ifplugd package installed.