netifd: do not set uptime as part of interface data in dhcp.script

Cherry-picks: 76d3ec27 Setting uptime as part of interface data in dhcp script leads to unnecessary hotplug with IFUPDATE_DATA being set on every dhcp renew. This has unwanted consequences, for example, of firewall reload even though no dhcp related data had changed.

Therefore, this logic is being removed from this script.