clk: k6x: Modify clock_init to enable external RMII clock source
clk: k6x: Modify clock_init to enable external RMII clock source

This change enables the RMII external clock source at the clock
initialization function.

Signed-off-by: Lukasz Majewski <7acbb0643e3da1a0f6f894ebd720fb3807e67dff@denx.de>

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