stm32/sdcard: Add sdcard_select_sd/mmc functions.

So that C code can select which of SD or MMC to use.

Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/sdcard.c

@@ -200,6 +200,14 @@ void sdcard_init(void) {
     #endif
 }
 
+void sdcard_select_sd(void) {
+    pyb_sdmmc_flags |= PYB_SDMMC_FLAG_SD;
+}
+
+void sdcard_select_mmc(void) {
+    pyb_sdmmc_flags |= PYB_SDMMC_FLAG_MMC;
+}
+
 STATIC void sdmmc_msp_init(void) {
     // enable SDIO clock
     SDMMC_CLK_ENABLE();

ports/stm32/sdcard.h

@@ -30,6 +30,8 @@
 #define SDCARD_BLOCK_SIZE (512)
 
 void sdcard_init(void);
+void sdcard_select_sd(void);
+void sdcard_select_mmc(void);
 bool sdcard_is_present(void);
 bool sdcard_power_on(void);
 void sdcard_power_off(void);