version: fix include
version: fix include

When including rte_version.h without string.h, there is a compilation error:
include/rte_version.h: error: implicit declaration of function ‘strlen’

Signed-off-by: Thomas Monjalon <ee2fa8b2681c737f775687e475dcbf2028a412f1@6wind.com>

tsphillips/dpdk-fork,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,msune/dpdk,venkynv/dpdk-mirror,venkynv/dpdk-mirror,venkynv/dpdk-mirror,mixja/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,mixja/dpdk,msune/dpdk,msune/dpdk,tsphillips/dpdk-fork,tsphillips/dpdk-fork,john-mcnamara-intel/dpdk,msune/dpdk,mixja/dpdk,tsphillips/dpdk-fork,mixja/dpdk