hash: fix return of bulk lookup

hash: fix return of bulk lookup

The __rte_hash_lookup_bulk() function returns void, and therefore
should not return with an expression. This commit fixes the following
compiler warning when attempting to compile with "-pedantic -std=c11".

  warning: ISO C forbids ‘return’ with expression, in function
           returning void [-Wpedantic]

Fixes: 9eca8bd7a61c ("hash: separate lock-free and r/w lock lookup")
Cc: stable@dpdk.org
Signed-off-by: Jeff Shaw <jeffrey.b.shaw@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>