mempool: remove redundant socket id assignment

mempool: remove redundant socket id assignment

There is a redundant repetition mempool socket_id assignment in the
file rte_mempool.c in function rte_mempool_create_empty. The
statement "mp->socket_id = socket_id;"appear twice in line 821
and 824. One of them is redundant, so delete it.

Fixes: 85226f9c526b ("mempool: introduce a function to create an empty pool")

Signed-off-by: Wei Zhao <wei.zhao1@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>