examples/qos_sched: fix build for less lcores

examples/qos_sched: fix build for less lcores

APP_MAX_LCORES is hardcoded as 64.
This will cause build err when RTE_MAX_LCORE is less then 64.

"args.c:127:22: error: iteration 8 invokes undefined behavior
	[-Werror=aggressive-loop-optimizations]
   if (cfg->lcore_role[i] == ROLE_RTE)
       ~~~~~~~~~~~~~~~^~~
args.c:126:2: note: within this loop
  for (i = 0; i < APP_MAX_LCORE; i++) {"

Fixes: d52b5e735aa3 ("examples/qos_sched: fix lcore limit")
Cc: stable@dpdk.org
Signed-off-by: Hemant Agrawal <hemant.agrawal@nxp.com>