stm32/system_stm32: Allow selection of OSPI clock source.

Added a #if-block to `system_stm32.c` to check whether
`MICROPY_HW_RCC_OSPI_CLKSOURCE` is defined.  If that is the case, the
clock source for the OSPI will be changed to the specified source.

Signed-off-by: nspsck <[email protected]>

Author: nspsck

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;