net/cxgbe: fix double MPS alloc by flow validate and create

net/cxgbe: fix double MPS alloc by flow validate and create

The Multi Port Switch (MPS) entry is allocated twice when both
flow validate and create are invoked, but only freed once during
flow destroy. Avoid double alloc by moving MPS entry allocation
closer to when the filter create request is sent to hardware and
will be ignored for filter validate request.

Fixes: fefee7a619a4 ("net/cxgbe: add flow ops to match based on dest MAC")
Cc: stable@dpdk.org
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>