drivers: pwm: Adding a flag to allow build for stm32l1 series
drivers: pwm: Adding a flag to allow build for stm32l1 series

Include a flag to allow build for stm32l1 series

Signed-off-by: Sidhdharth Yadav <f6e96f94296714fddae5bdd9b16f23c1fbc6fcc6@hcl.com>

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