For rx filter 'HWTSTAMP_FILTER_PTP_V2_EVENT', it should be
PTP v2/802.AS1, any layer, any kind of event packet, but HW only
take timestamp snapshot for below PTP message: sync, Pdelay_req,
Pdelay_resp.

Then it causes below issue when test E2E case:
ptp4l[2479.534]: port 1: received DELAY_REQ without timestamp
ptp4l[2481.423]: port 1: received DELAY_REQ without timestamp
ptp4l[2481.758]: port 1: received DELAY_REQ without timestamp
ptp4l[2483.524]: port 1: received DELAY_REQ without timestamp
ptp4l[2484.233]: port 1: received DELAY_REQ without timestamp
ptp4l[2485.750]: port 1: received DELAY_REQ without timestamp
ptp4l[2486.888]: port 1: received DELAY_REQ without timestamp
ptp4l[2487.265]: port 1: received DELAY_REQ without timestamp
ptp4l[2487.316]: port 1: received DELAY_REQ without timestamp

Timestamp snapshot dependency on register bits in received path:
SNAPTYPSEL TSMSTRENA TSEVNTENA 	PTP_Messages
01         x         0          SYNC, Follow_Up, Delay_Req,
                                Delay_Resp, Pdelay_Req, Pdelay_Resp,
                                Pdelay_Resp_Follow_Up
01         0         1          SYNC, Pdelay_Req, Pdelay_Resp

For dwmac v5.10a, enabling all events by setting register
DWC_EQOS_TIME_STAMPING[SNAPTYPSEL] to 2’b01, clearing bit [TSEVNTENA]
to 0’b0, which can support all required events.
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>