STM32L1 - Enable the low power timer

Enable the low power timer for the NUCLEO_L152RE

Author: svastm

hal/targets.json

@@ -965,7 +965,7 @@
         "inherits": ["Target"],
         "progen": {"target": "nucleo-l152re"},
         "detect_code": ["0710"],
-        "device_has": ["ANALOGIN", "ANALOGOUT", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SERIAL_FC", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
+        "device_has": ["ANALOGIN", "ANALOGOUT", "I2C", "I2CSLAVE", "INTERRUPTIN", "LOWPOWERTIMER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SERIAL_FC", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
         "release_versions": ["2", "5"]
     },
     "NUCLEO_L432KC": {