net/i40e: fix Rx data segment buffer length

net/i40e: fix Rx data segment buffer length

Buffer length be configured for each data segment should not exceed
the requested value, or device may fill data that exceed the boundary
of memory that be reserved.

Fixes: 4861cde46116 ("i40e: new poll mode driver")
Cc: stable@dpdk.org
Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Reviewed-by: Mark Kavanagh <mark.b.kavanagh@intel.com>
Tested-by: Mark Kavanagh <mark.b.kavanagh@intel.com>