Add a check to ensure that all shift counts are valid.
Shifting by more than 63 bits may result in undefined behavior, as
noted during coverity scan.
Coverity issue: 376527
Fixes: e697f35dbd ("event/dlb2: update rolling mask used for dequeue")
Cc: stable@dpdk.org
Signed-off-by: Timothy McDaniel <timothy.mcdaniel@intel.com>