doc: release notes: gptp clock sync ratio change
doc: release notes: gptp clock sync ratio change

Mention that the gptp clock sync ratio is now a double instead of a
float.

Signed-off-by: Xabier Marquiegui <dbea95d49f9624e3bb4209dcacd8aa8b65ad3472@ainguraiiot.com>

zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr