ptp: ocp: fix PPS source selector debugfs reporting

The NTL timecard design has a PPS1 selector which selects the
the PPS source automatically, according to Section 1.9 of the
documentation.

  If there is a SMA PPS input detected:
     - send signal to MAC and PPS slave selector.

  If there is a MAC PPS input detected:
     - send GNSS1 to the MAC
     - send MAC to the PPS slave

  If there is a GNSS1 input detected:
     - send GNSS1 to the MAC
     - send GNSS1 to the PPS slave.MAC

Change the debugfs summary so it reflects the correct mapping,
for assistance in debugging.  No functional change.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>