stmmac: fix ptp header for GMAC3 hw timestamp

According the CYCLON V documention only the bit 16 of snaptypesel should
set.
(more information see Table 17-20 (cv_5v4.pdf) :
 Timestamp Snapshot Dependency on Register Bits)

Fixes: d2042052a0aa ("stmmac: update the PTP header file")
Signed-off-by: Mario Molitor <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
2 files changed