doc: releases: 2.4: Add USB detailed changes.
doc: releases: 2.4: Add USB detailed changes.

Add a entry to 2.4 release notes about a need to explicitly
call usb_enable() for applications that configures specific
features.

Signed-off-by: Emil Obalski <a38006c9a9911dcd7c7e26537de6a2fa1043ca9e@nordicsemi.no>

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