Add support for ffat on 4MB ESP32 Dev Module and mhetesp32minikit board. (#2588)

* Update boards.txt

Add menu items for ffat on mhetesp32minikit board.

* Add partition table.

* Added ffat partition for 4MB ESP32 Dev Module.

* Added comment about partitioning schemes.

boards.txt

@@ -64,8 +64,10 @@ esp32.menu.PSRAM.disabled.build.defines=
 esp32.menu.PSRAM.enabled=Enabled
 esp32.menu.PSRAM.enabled.build.defines=-DBOARD_HAS_PSRAM -mfix-esp32-psram-cache-issue
 
-esp32.menu.PartitionScheme.default=Default
+esp32.menu.PartitionScheme.default=Default with spiffs (4MB FLASH)
 esp32.menu.PartitionScheme.default.build.partitions=default
+esp32.menu.PartitionScheme.defaultffat=Default with ffat (4MB FLASH)
+esp32.menu.PartitionScheme.defaultffat.build.partitions=default_ffat
 esp32.menu.PartitionScheme.minimal=Minimal (2MB FLASH)
 esp32.menu.PartitionScheme.minimal.build.partitions=minimal
 esp32.menu.PartitionScheme.no_ota=No OTA (Large APP)
@@ -1555,8 +1557,10 @@ mhetesp32minikit.menu.FlashFreq.80.build.flash_freq=80m
 mhetesp32minikit.menu.FlashFreq.40=40MHz
 mhetesp32minikit.menu.FlashFreq.40.build.flash_freq=40m
 
-mhetesp32minikit.menu.PartitionScheme.default=Default
+mhetesp32minikit.menu.PartitionScheme.default=Default with spiffs
 mhetesp32minikit.menu.PartitionScheme.default.build.partitions=default
+mhetesp32minikit.menu.PartitionScheme.defaultffat=Default with ffat
+mhetesp32minikit.menu.PartitionScheme.defaultffat.build.partitions=default_ffat
 mhetesp32minikit.menu.PartitionScheme.no_ota=No OTA (Large APP)
 mhetesp32minikit.menu.PartitionScheme.no_ota.build.partitions=no_ota
 mhetesp32minikit.menu.PartitionScheme.no_ota.upload.maximum_size=2097152

libraries/FFat/examples/FFat_Test/FFat_Test.ino

 #include "FS.h"
 #include "FFat.h"
 
+// This file should be compiled with 'Partition Scheme' (in Tools menu)
+// set to 'Default with ffat' if you have a 4MB ESP32 dev module or
+// set to '16M Fat' if you have a 16MB ESP32 dev module.
+
 // You only need to format FFat the first time you run a test
 #define FORMAT_FFAT true
 

tools/partitions/default_ffat.csv

+# Name,   Type, SubType, Offset,  Size, Flags
+nvs,      data, nvs,     0x9000,  0x5000,
+otadata,  data, ota,     0xe000,  0x2000,
+app0,     app,  ota_0,   0x10000, 0x140000,
+app1,     app,  ota_1,   0x150000,0x140000,
+eeprom,   data, 0x99,    0x290000,0x1000,
+ffat,     data, fat,     0x291000,0x16F000,