system(u0): update STM32U0xx system

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

Author: fpistm

system/STM32U0xx/system_stm32u0xx.c

@@ -309,7 +309,7 @@ void SystemCoreClockUpdate(void)
   }
   /* Compute HCLK clock frequency --------------------------------------------*/
   /* Get HCLK prescaler */
-  tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4U) & 0xFU];
+  tmp = AHBPrescTable[(((RCC->CFGR & RCC_CFGR_HPRE) >> RCC_CFGR_HPRE_Pos) & 0xFU)];
   /* HCLK clock frequency */
   SystemCoreClock >>= tmp;
 }