Added alternate function inits for USART

SHAL/Src/System/system_stm32f0xx.c

@@ -91,11 +91,6 @@
   */
   /* This variable is updated in three ways:
       1) by calling CMSIS function SystemCoreClockUpdate()
-      2) by calling HAL API function HAL_RCC_GetHCLKFreq()
-      3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
-         Note: If you use this function to configure the system clock; then there
-               is no need to call the 2 first functions listed above, since SystemCoreClock
-               variable is updated automatically.
   */
 uint32_t SystemCoreClock = 8000000;