Function SystemClockHSE_Config

* @brief Switch the PLL source from HSI48 to HSI, and select the PLL as SYSCLK * source. * The system Clock is configured as follows : * System Clock source = PLL (HSI) * SYSCLK(Hz) = 48000000 * HCLK(Hz) = 48000000 * AHB Prescaler = 1 * APB1 Prescaler