stm32/system_stm32: Allows OSPI-clocksource selection.

Added a if-statement to system_stm32.c to check whether
MICROPY_HW_RCC_OSPI_CLKSOURCE is defined. If that was
the case, the clocksource for the OSPI will be changed
to the specified source.

Signed-off-by: nspsck <teng.jiang94@gmail.com>

ports/stm32/system_stm32.c

@@ -461,6 +461,11 @@ MP_WEAK void SystemClock_Config(void) {
     PeriphClkInitStruct.QspiClockSelection = MICROPY_HW_RCC_QSPI_CLKSOURCE;
     #endif
 
+    #if defined(MICROPY_HW_RCC_OSPI_CLKSOURCE)
+    PeriphClkInitStruct.PeriphClockSelection |= RCC_PERIPHCLK_OSPI;
+    PeriphClkInitStruct.OspiClockSelection = MICROPY_HW_RCC_OSPI_CLKSOURCE;
+    #endif
+
     #if defined(MICROPY_HW_RCC_SPI123_CLKSOURCE)
     PeriphClkInitStruct.PeriphClockSelection |= RCC_PERIPHCLK_SPI123;
     PeriphClkInitStruct.Spi123ClockSelection = MICROPY_HW_RCC_SPI123_CLKSOURCE;