ptp: ocp: Fix PTP_PF_* verification requests

Update and check functionality for pin configuration requests:

PTP_PF_NONE: requests "IN: None", disabling the pin.

  # testptp -d /dev/ptp3 -L3,0 -i1
  set pin function okay
  # cat sma4
  IN: None

PTP_PF_EXTTS: should configure external timestamps, but since the
timecard can steer inputs to multiple inputs as well as timestamps,
allow the request, but don't change configurations.

  # testptp -d /dev/ptp3 -L3,1 -i1
  set pin function okay

  (no functional or configuration change here yet)

PTP_PF_PEROUT: Channel 0 is the PHC, at 1PPS.  Channels 1-4 are
the programmable frequency generators.

  # fails because period is not 1PPS.
  # testptp -d /dev/ptp3 -L3,2 -i0  -p 500000000
  PTP_PEROUT_REQUEST: Invalid argument

  # testptp -d /dev/ptp3 -L3,2 -i0  -p 1000000000
  periodic output request okay
  # cat sma4
  OUT: PHC

  # testptp -d /dev/ptp3 -L3,2 -i1 -p 500000000 -w 200000000
  periodic output request okay
  # cat sma4
  OUT: GEN1
  # cat gen1/signal
  500000000 40 0 1 2022-03-10T23:55:26 TAI
  # cat gen1/running
  1

  # testptp -d /dev/ptp3 -L3,2 -i1 -p 0
  periodic output request okay
  # cat gen1/running
  0

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Link: https://lore.kernel.org/r/20220315194626.1895-1-jonathan.lemon@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>