net/i40e: fix setting TPID with AQ command

net/i40e: fix setting TPID with AQ command

TPID can be set by set_switch_config AdminQ command on
new FW release. But find fail to set 0x88A8 on some NICs.
According to the datasheet, Switch Tag value should not
be identical to either the First Tag or Second Tag values.
So set something other than common Ethertype for internal
switching.

Fixes: 73cd7d6dc8e1 ("net/i40e: use set switch AQ instead of register setting")
Cc: stable@dpdk.org
Signed-off-by: Beilei Xing <beilei.xing@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>