examples/qos_sched: fix negative loop bound in option parsing
examples/qos_sched: fix negative loop bound in option parsing

negative_returns: Using unsigned variable n_tokens in a loop exit condition.

Coverity issue: 30704
Fixes: de3cfa2c9823 ("sched: initial import")

Signed-off-by: Slawomir Mrozowicz <e88e38a554fa6ee2c1af7d54e8bb48581354aa35@intel.com>
Acked-by: Cristian Dumitrescu <25468b8a3698eeb3c368247f8635924bb4a1ce2c@intel.com>

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