bdk: use f_unmount instead of null f_mount

bdk/storage/ramdisk.c

@@ -44,7 +44,7 @@ int ram_disk_init(void *ram_fs, u32 ramdisk_size)
 		disk_set_info(DRIVE_RAM, SET_SECTOR_COUNT, &ramdisk_size);
 
 		// Unmount ramdisk.
-		f_mount(NULL, "ram:", 1);
+		f_unmount("ram:");
 
 		// Format as exFAT w/ 32KB cluster with no MBR.
 		res = f_mkfs("ram:", FM_EXFAT | FM_SFD, RAMDISK_CLUSTER_SZ, buf, 0x400000);

bdk/storage/sd.c

@@ -227,7 +227,7 @@ static void _sd_deinit(bool deinit)
 	if (sd_init_done)
 	{
 		if (sd_mounted)
-			f_mount(NULL, "sd:", 1); // Volume 0 is SD.
+			f_unmount("sd:", 1); // Volume 0 is SD.
 
 		if (deinit)
 		{