net: stmmac: Only update the auto-discovered PTP clock features

net: stmmac: Only update the auto-discovered PTP clock features

Some DWMAC variants such as dwmac1000 don't support discovering the
number of output pps and auxiliary snapshots. Allow these parameters to
be defined in default ptp_clock_info, and let them be updated only when
the feature discovery yielded a result.

Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20241112170658.2388529-4-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>