sdmmc: Refactor again

- Refactor various variables and defines
- Removed Card/BGA and OEM ID info as they are static and useless
- Commented out bkops functions completely as not used
- Remove extra buf usage when there's already storage for storing that data
- Optimize various functions to save space
- Clean up useless or duplicate code

bdk/storage/nx_sd.h

@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2018 naehrwert
- * Copyright (c) 2018-2019 CTCaer
+ * Copyright (c) 2018-2021 CTCaer
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions of the GNU General Public License,
@@ -45,6 +45,7 @@ extern FATFS sd_fs;
 void sd_error_count_increment(u8 type);
 u16 *sd_get_error_count();
 bool sd_get_card_removed();
+bool sd_get_card_initialized();
 u32  sd_get_mode();
 int  sd_init_retry(bool power_cycle);
 bool sd_initialize(bool power_cycle);