net: phy: micrel: move the PHY timestamping check

Both lan8814_ptp_init() and lan8814_ptp_probe_once() are only used if
PTP and PHY timestamping is enabed. Up until now the probe function just
returns early, if they are not needed. But we need the
phy_package_init_once() functionality for the coma mode GPIO setup. Move
the check into the functions itself.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>