sys/modules/dpdk_lpm4: do not build without INET

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1236

(cherry picked from commit 304a03275a65cf811fb6c06fa1c37783d07c99a4)
(cherry picked from commit 040a7e0dcbc234aa66d0b4b53638db12b81a7b75)
Approved-by: re (cperciva)