cfgfile: fix return value comment
cfgfile: fix return value comment

Function rte_cfgfile_load can return NULL value, when something goes wrong.

Signed-off-by: Dmitriy Yakovlev <2d110721a760274102d892c7c9df80aa1871b13a@gmail.com>
Acked-by: Cristian Dumitrescu <25468b8a3698eeb3c368247f8635924bb4a1ce2c@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk