net: stmmac: skip only stmmac_ptp_register when resume from suspend

When resume from suspend, besides skipping PTP registration, it also
skipping PTP HW initialization. This could cause PTP clock not able to
operate properly when resume from suspend.

To fix this, only stmmac_ptp_register() is skipped when resume from
suspend.

Fixes: fe131929

 ("stmmac: Don't init ptp again when resume from suspend/hibernation")
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>