ptp: Allow exposing cycles only for clocks with free-running counter

ptp: Allow exposing cycles only for clocks with free-running counter

The PTP core falls back to gettimex64 and getcrosststamp when
getcycles64 or getcyclesx64 are not implemented. This causes the CYCLES
ioctls to retrieve PHC real time instead of free-running cycles.

Reject PTP_SYS_OFFSET_{PRECISE,EXTENDED}_CYCLES for clocks without
free-running counter support since the result would represent PHC real
time and system time rather than cycles and system time.

Fixes: faf23f54d366 ("ptp: Add ioctl commands to expose raw cycle counter values")
Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20251029083813.2276997-1-cjubran@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>