stm32/stm32_it: Fix RTC macro.

Signed-off-by: iabdalkader <i.abdalkader@gmail.com>

Author: iabdalkader

ports/stm32/stm32_it.c

@@ -582,7 +582,9 @@ void RTC_WKUP_IRQHandler(void)
     RTC->ISR &= ~RTC_ISR_WUTF; // clear wakeup interrupt flag
     #endif
     Handle_EXTI_Irq(EXTI_RTC_WAKEUP); // clear EXTI flag and execute optional callback
+    #ifdef __HAL_RTC_WAKEUPTIMER_EXTI_CLEAR_FLAG
     __HAL_RTC_WAKEUPTIMER_EXTI_CLEAR_FLAG(); // Clear the EXTI's line Flag for RTC WakeUpTimer
+    #endif
     IRQ_EXIT(RTC_WKUP_IRQn);
 }
 #endif