[NUCLEO_F070RB] Set NVIC Timer priorities

This fix is a solution for issue #816 when having two separate IRQ handlers
in Timers (UPDATE Irq and OutputCompare Irq). The update priority needs to
be higher to avoid undefined behaviours.

Change-Id: I5ef2c27926167ed22108901cd63586692a5f8f90

Author: Maciej Bojczuk

hal/targets/cmsis/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F070RB/hal_tick.c

@@ -130,8 +130,10 @@ HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority) {
     // Output compare channel 2 interrupt for HAL tick
     NVIC_SetVector(TIM_MST_UP_IRQ, (uint32_t)timer_update_irq_handler);
     NVIC_EnableIRQ(TIM_MST_UP_IRQ);
+    NVIC_SetPriority(TIM_MST_UP_IRQ, 0);
     NVIC_SetVector(TIM_MST_OC_IRQ, (uint32_t)timer_oc_irq_handler);
     NVIC_EnableIRQ(TIM_MST_OC_IRQ);
+    NVIC_SetPriority(TIM_MST_OC_IRQ, 1);
 
     // Enable interrupts
     __HAL_TIM_ENABLE_IT(&TimMasterHandle, TIM_IT_UPDATE); // For 32-bit counter