AP_Filesystem: use wear levelling sector size for ESP32 FlashFS

[muramura]

Summary

Use the wear levelling sector size when the ESP32 filesystem uses FlashFS.

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

Description

AP_Filesystem_ESP32::disk_free() and disk_space() currently always
convert the FatFs sector count using FF_SS_SDCARD.

When HAL_ESP32_FLASHFS is defined, the filesystem uses ESP-IDF wear
levelling, so the correct sector size is FF_SS_WL.

This change selects:

• FF_SS_WL for FlashFS
• FF_SS_SDCARD otherwise

The existing SD card behavior is unchanged.

Testing

Built Copter for esp32buzz with the normal filesystem configuration:

• AP_FILESYSTEM_ESP32_ENABLED=1
• HAL_ESP32_FLASHFS not defined
• build passed

Built Copter for esp32buzz with:

define HAL_ESP32_FLASHFS 1

supplied through --extra-hwdef, verifying the FF_SS_WL build path.

Both builds completed successfully.

git diff --check upstream/master also passed.