Changed SD library for nrf52 and got S&F working (#6382)

- Changed library from deprecated arduino SD library to wrapper of SdFat library
- Fixed some bugs in the S&F code for SD card storage
Now the S&F functionality works on nrf52 (tested on rak4631 with RAK15002)

variants/rak4631/platformio.ini

@@ -20,7 +20,7 @@ lib_deps =
   https://github.com/RAKWireless/RAK13800-W5100S.git#1.0.2
   rakwireless/RAKwireless NCP5623 RGB LED library@^1.0.2
   https://github.com/RAKWireless/RAK12034-BMX160.git#dcead07ffa267d3c906e9ca4a1330ab989e957e2
-  https://github.com/Woutvstk/arduino_SD.git#909c2a4a14f5b053bb69958709f0c874aa358c38 ;library to acces SD card
+  https://github.com/Woutvstk/SdFat_wrapper25.git#6f8f48d56c15cbeac753560dfeede4a487f81f4c
 
 ; If not set we will default to uploading over serial (first it forces bootloader entry by talking 1200bps to cdcacm)
 ; Note: as of 6/2013 the serial/bootloader based programming takes approximately 30 seconds

variants/rak4631/variant.h

@@ -138,6 +138,12 @@ static const uint8_t SCK = PIN_SPI_SCK;
 #define SPI_MISO PIN_SPI1_MISO
 #define SDCARD_CS (26)
 
+// Some settings for the SdFat library to optimize flash usage
+#define SDFAT_FILE_TYPE 1 // only support FAT16/FAT32, not exFAT
+#define CHECK_FLASH_PROGRAMMING                                                                                                  \
+    0 // this reduces flash usage but may cause higher power usage when sd card is idle TODO:Check if power usage is higher
+#define MAINTAIN_FREE_CLUSTER_COUNT 1 // maintain free cluster count
+
 /*
  * eink display pins
  */