dts/arm: STM32: Adding flash clock settings in dtsi for stm32wb series.
dts/arm: STM32: Adding flash clock settings in dtsi for stm32wb series.

This patch adds flash clock settings in device tree for stm32wb
series so that the stm32 flash driver can get the clock settings
from this dtsi file.

Signed-off-by: Krishna Mohan Dani <2f92acbcef6b57b10df043e51f4a57d8454f58b9@hcl.com>

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