In the previous code, the gptp flag was completely related to
the !dir_tx in struct rswitch_gwca_queue because
rswitch_gwca_queue_alloc() was called below:

< In rswitch_txdmac_alloc() >
err = rswitch_gwca_queue_alloc(ndev, priv, rdev->tx_queue, true, false,
			      TX_RING_SIZE);
So, dir_tx = true, and gptp = false.

< In rswitch_rxdmac_alloc() >
err = rswitch_gwca_queue_alloc(ndev, priv, rdev->rx_queue, false, true,
			      RX_RING_SIZE);
So, dir_tx = false, and gptp = true.

In the future, a new queue handling for timestamp will be implemented
and this gptp flag is confusable. So, remove the gptp flag.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>