examples/qos_sched: fix core mask overflow

examples/qos_sched: fix core mask overflow

Masking of core mask was incorrect. Instead of using 1U for shifting, it
should be using 1LU as the result is assigned to uint64.

CID 375859: Potentially overflowing expression "1U << app_main_core" with
type "unsigned int" (32 bits, unsigned) is evaluated using 32-bit
arithmetic, and then used in a context that expects an expression of
type "uint64_t" (64 bits, unsigned).

Coverity issue: 375859
Fixes: de3cfa2c9823 ("sched: initial import")
Cc: stable@dpdk.org
Signed-off-by: Megha Ajmera <megha.ajmera@intel.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>