system(u3): update STM32U3xx hal default config

Allow some redefinition.

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

Author: fpistm

system/STM32U3xx/stm32u3xx_hal_conf_default.h

@@ -183,10 +183,18 @@ extern "C" {
 /**
   * @brief This is the HAL system configuration section
   */
+#if !defined  (VDD_VALUE)
 #define  VDD_VALUE                    3300UL /*!< Value of VDD in mv */
+#endif /* VDD_VALUE */
+#if !defined  (TICK_INT_PRIORITY)
 #define  TICK_INT_PRIORITY            ((1UL<<__NVIC_PRIO_BITS) - 1UL)  /*!< tick interrupt priority (lowest by default) */
+#endif /* TICK_INT_PRIORITY */
+#if !defined  (USE_RTOS)
 #define  USE_RTOS                     0U
+#endif /* USE_RTOS */
+#if !defined  (PREFETCH_ENABLE)
 #define  PREFETCH_ENABLE              1U               /*!< Enable prefetch */
+#endif /* PREFETCH_ENABLE */
 
 /* ########################## Assert Selection ############################## */
 /**