drivers/flash: STM32: Adding condition to enable HSI clock for L1 series.
drivers/flash: STM32: Adding condition to enable HSI clock for L1 series.

This commit adds changes to enable HSI clock for stm32l1 series.

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

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