[PWR] Allow to enable HAL module only

Define `HAL_RTC_MODULE_ONLY` in `build_opt.h` or `hal_conf_extra.h`
allow HAL PWR module usage without any usage by the core.

Fixes stm32duino#697

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/low_power.c

@@ -39,7 +39,7 @@
 #include "Arduino.h"
 #include "low_power.h"
 
-#ifdef HAL_PWR_MODULE_ENABLED
+#if defined(HAL_PWR_MODULE_ENABLED) && !defined(HAL_PWR_MODULE_ONLY)
 
 #ifdef __cplusplus
 extern "C" {
@@ -346,6 +346,6 @@ WEAK void SystemClock_ConfigFromStop(void)
 }
 #endif
 
-#endif /* HAL_PWR_MODULE_ENABLED */
+#endif /* HAL_PWR_MODULE_ENABLED  && !HAL_PWR_MODULE_ONLY */
 
 /************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

cores/arduino/stm32/low_power.h

@@ -43,7 +43,7 @@
 #include "stm32_def.h"
 #include "uart.h"
 
-#ifdef HAL_PWR_MODULE_ENABLED
+#if defined(HAL_PWR_MODULE_ENABLED) && !defined(HAL_PWR_MODULE_ONLY)
 
 #ifdef __cplusplus
 extern "C" {
@@ -67,6 +67,6 @@ void SystemClock_ConfigFromStop(void);
 }
 #endif
 
-#endif /* HAL_PWR_MODULE_ENABLED */
+#endif /* HAL_PWR_MODULE_ENABLED  && !HAL_PWR_MODULE_ONLY */
 
 #endif /* __LOW_POWER_H */