ptp: ocp: Limit signal/freq counts in summary output functions

ptp: ocp: Limit signal/freq counts in summary output functions

The debugfs summary output could access uninitialized elements in
the freq_in[] and signal_out[] arrays, causing NULL pointer
dereferences and triggering a kernel Oops (page_fault_oops).
This patch adds u8 fields (nr_freq_in, nr_signal_out) to track the
number of initialized elements, with a maximum of 4 per array.
The summary output functions are updated to respect these limits,
preventing out-of-bounds access and ensuring safe array handling.

Widen the label variables because the change confuses GCC about
max length of the strings.

Fixes: ef61f5528fca ("ptp: ocp: add Adva timecard support")
Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250514073541.35817-1-maimon.sagi@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>