stm32: STM32H7_CORE V10 uses SDMMC2 for SD card

  The V10 hardware revision routes the SD card to SDMMC2 (pins B14, B15,
  B3, B4, D6, D7) instead of SDMMC1. Without MICROPY_HW_SDCARD_SDMMC=2
  the driver looks up those pins in the SDMMC1 AF table and fails to
  build.

Author: Nunzio Raciti

ports/stm32/boards/STM32H7_CORE/mpconfigboard.h

@@ -53,7 +53,8 @@ extern void lv_deinit(void);
 #endif
 
 #if defined(BOARD_V10)
-// GPIO SDCARD
+// GPIO SDCARD (SDMMC2)
+#define MICROPY_HW_SDCARD_SDMMC (2)
 #define MICROPY_HW_SDCARD_D0    (pin_B14)
 #define MICROPY_HW_SDCARD_D1    (pin_B15)
 #define MICROPY_HW_SDCARD_D2    (pin_B3)