drivers/clock_control: stm32: Move CLOCK_STM32_HSE_CLOCK definition
drivers/clock_control: stm32: Move CLOCK_STM32_HSE_CLOCK definition

Symbol CLOCK_STM32_HSE_CLOCK will remain in use in context of stm32
clock_control configuration using device tree, cf commit
a7989f64a351caaf4db785e83ceaf9a086d4e8e3.

In preparation for next change, separate it from the others symbols
definition. Also make it non dependent from other Kconfig symbols.

Signed-off-by: Erwan Gouriou <de4d967452b83bb0e37525652734e7d9163b6a4c@linaro.org>

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