ptp: ocp: constify 'struct bin_attribute'

The sysfs core now allows instances of 'struct bin_attribute' to be
moved into read-only memory. Make use of that to protect them against
accidental or malicious modifications.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20241222-sysfs-const-bin_attr-ptp-v1-1-5c1f3ee246fb@weissschuh.net


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