mempool: fix get function documentation

static function `rte_mempool_do_generic_get()` returns zero on success,
not >=0 as its function comment documents.

Since this function called by public API, the comment causes confusion
on the public API return value.

Fixing the internal function documentation for return value.

Fixes: af75078 ("first public release")
Cc: stable@dpdk.org

Reported-by: Mahesh Adulla <mahesh.adulla@amd.com>
Signed-off-by: Ferruh Yigit <ferruh.yigit@amd.com>
Reviewed-by: Morten Brørup <mb@smartsharesystems.com>
Acked-by: Huisong Li <lihuisong@huawei.com>

.mailmap

@@ -839,6 +839,7 @@ Maciej Rabeda <maciej.rabeda@intel.com>
 Maciej Szwed <maciej.szwed@intel.com>
 Madhu Chittim <madhu.chittim@intel.com>
 Madhuker Mythri <madhuker.mythri@oracle.com>
+Mahesh Adulla <mahesh.adulla@amd.com>
 Mahipal Challa <mchalla@marvell.com>
 Mah Yock Gen <yock.gen.mah@intel.com>
 Mairtin o Loingsigh <mairtin.oloingsigh@intel.com>

lib/mempool/rte_mempool.h

@@ -1484,7 +1484,7 @@ rte_mempool_put(struct rte_mempool *mp, void *obj)
  * @param cache
  *   A pointer to a mempool cache structure. May be NULL if not needed.
  * @return
- *   - >=0: Success; number of objects supplied.
+ *   - 0: Success.
  *   - <0: Error; code of driver dequeue function.
  */
 static __rte_always_inline int