Don't pass the mmc struct around

fusee/fusee-primary/src/sd_utils.h

@@ -3,11 +3,8 @@
 
 #include "utils.h"
 #include "sdmmc.h"
-#include "lib/fatfs/ff.h"
-
-void save_sd_state(void **mmc);
-void resume_sd_state(void *mmc);
 
+int initialize_sd(void);
 size_t read_sd_file(void *dst, size_t dst_size, const char *filename);
 
 #endif