distributor: enhance and fix tag matching

distributor: enhance and fix tag matching

With introduction of in_flight_bitmask, the whole 32 bits of tag can be
used. Further more, this patch fixed the integer overflow when finding
the matched tags.
The maximum number workers is now defined as 64, which is length of
double-word. The link between number of workers and RTE_MAX_LCORE is
now removed. Compile time check is added to ensure the
RTE_DISTRIB_MAX_WORKERS is less than or equal to size of double-word.

Signed-off-by: Qinglai Xiao <jigsaw@gmail.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>