stm32/sdcard: Use maximum speed SDMMC clock on F7 MCUs.

This will get the SDMMC clock up to 48MHz.

ports/stm32/sdcard.c

@@ -198,6 +198,10 @@ bool sdcard_power_on(void) {
     }
 
     // configure the SD bus width for wide operation
+    #if defined(MCU_SERIES_F7)
+    // use maximum SDMMC clock speed on F7 MCUs
+    sd_handle.Init.ClockBypass = SDMMC_CLOCK_BYPASS_ENABLE;
+    #endif
     if (HAL_SD_ConfigWideBusOperation(&sd_handle, SDIO_BUS_WIDE_4B) != HAL_OK) {
         HAL_SD_DeInit(&sd_handle);
         goto error;