ptp: ocp: Add serial port information to the debug summary

On the debug summary page, show the /dev/ttyS<port> mapping.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Link: https://lore.kernel.org/r/20220304054615.1737-1-jonathan.lemon@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>