fix typo in DHCP config

DHCP server - start: Job failed to start

carbon dhcpd: Configuration file errors encountered

linux-host-entries.ttyS1-115200 line 1450:
expecting a network hardware type

follow-up to I79fd5d8424d4f

Change-Id: I01154ffe8d55d2965a7a03bb3fda8e9197e04781