mem: fix resize return handling for --single-file-segments

resize_hugefile() returns either 0 (which indicates success) or -1
(which indicates failure). We failed to check the success as we
use --single-file-segments option.

Fixes: 2a04139f66b4 ("eal: add single file segments option")

Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>