Add TX/RX timestamp tracking for rpmsg_port to enable latency
measurement and debugging:
- Add rpmsg_port_get_timestamp() to retrieve buffer timestamps
- Add rpmsg_port_update_timestamp() to record timestamps at TX/RX time
- Integrate timestamp recording in rpmsg_port_spi and rpmsg_port_spi_slave
- Reserve space for rpmsg_timestamp_s in buffer size calculations
Signed-off-by: liaoao <liaoao@xiaomi.com>
liaoao
425a760799