ptp: ocp: Have Kconfig select NET_DEVLINK

NET doesn't imply NET_DEVLINK.  Select this separately, so that
random config combinations don't complain.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 773bda96

 ("ptp: ocp: Expose various resources on the timecard.")
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>