net: ptp: Add TIME_RECEIVER_ONLY feature

Implement possibility to configure PTP stack in TIME_RECEIVER_ONLY mode.
This restrics stack behaviour and doesn't allow for any PTP Port
of the PTP Clock become a TimeTransmitter Clock.

The change includes:
- Kconfig option
- Additional field in `struct ptp_port` structure
- New state machine function for a timeReceiver-only PTP Port.
- Extra steps in PTP Clock and PTP Port initialization.

New finite state machine is based on the figure 31
in section 9.2.5 of the IEEE 1588-2019.

Signed-off-by: Adam Wojasinski <awojasinski@baylibre.com>