Merge branch 'ptp-Add-generic-helper-functions'

Kurt Kanzenbach says:

====================
ptp: Add generic helper functions

in order to reduce code duplication (and cut'n'paste errors) in the ptp code of
DSA, Ethernet and Phy drivers, create helper functions and move them to
ptp_classify. This way all drivers can share the same implementation.

This is version four and contains bugfixes. Implemented as discussed [1] [2]
[3] [4].

Previous versions can be found here:

 * https://lkml.kernel.org/netdev/20200723074946.14253-1-kurt@linutronix.de/
 * https://lkml.kernel.org/netdev/20200727090601.6500-1-kurt@linutronix.de/
 * https://lkml.kernel.org/netdev/20200730080048.32553-1-kurt@linutronix.de/

Thanks,
Kurt

Changes sinve v3:

 * Coding style issues (Richard Cochran, Petr Machata)
 * Add better documentation (Grygorii Strashko)
 * Fix cpts code (Grygorii Strashko)
 * Use ntohs() for TI code (Grygorii Strashko)
 * Add tags

Changes since v2:

 * Make ptp_parse_header() work in all scenarios (Russell King)
 * Fix msgtype offset for ptp v1 packets

Changes since v1:

 * Fix Kconfig (Richard Cochran)
 * Include more drivers (Richard Cochran)

[1] - https://lkml.kernel.org/netdev/20200713140112.GB27934@hoboy/
[2] - https://lkml.kernel.org/netdev/20200720142146.GB16001@hoboy/
[3] - https://lkml.kernel.org/netdev/20200723074946.14253-1-kurt@linutronix.de/
[4] - https://lkml.kernel.org/netdev/20200729100257.GX1551@shell.armlinux.org.uk/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>