STM: init timer once

Author: flippy84

targets/TARGET_STM/hal_tick_overrides.c

@@ -28,6 +28,8 @@ extern int mbed_sdk_inited;
 void init_16bit_timer(void);
 void init_32bit_timer(void);
 
+static bool initialized;
+
 #if TIM_MST_BIT_WIDTH <= 16
 static uint16_t prev_time;
 #else
@@ -40,11 +42,15 @@ static uint16_t prev_tick_remainder;
 
 HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority)
 {
+    if (initialized) {
+        return HAL_OK;
+    }
 #if TIM_MST_BIT_WIDTH == 16
     init_16bit_timer();
 #else
     init_32bit_timer();
 #endif
+    initialized = true;
     return HAL_OK;
 }