Merge branch 'net-stmmac-correctly-populate-ptp_clock_ops-getcrosststamp'

Russell King says:

====================
net: stmmac: correctly populate ptp_clock_ops.getcrosststamp

While reviewing code in the stmmac PTP driver, I noticed that the
getcrosststamp() method is always populated, irrespective of whether
it is implemented or not by the stmmac platform specific glue layer.

Where a platform specific glue layer does not implement it, the core
stmmac driver code returns -EOPNOTSUPP. However, the PTP clock core
code uses the presence of the method in ptp_clock_ops to determine
whether this facility should be advertised to userspace (see
ptp_clock_getcaps()).

Moreover, the only platform glue that implements this method is the
Intel glue, and for it not to return -EOPNOTSUPP, the CPU has to
support X86_FEATURE_ART.

This series updates the core stmmac code to only provide the
getcrosststamp() method in ptp_clock_ops when the platform glue code
provides an implementation, and then updates the Intel glue code to
only provide its implementation when the CPU has the necessary
X86_FEATURE_ART feature.
====================

Link: https://patch.msgid.link/aLhJ8Gzb0T2qpXBE@shell.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>