Fix the SPIFFS POSIX API (#489)
Fix the SPIFFS POSIX API (#489)

The commit ebdd2f9 defined some offsets to differentiate between the
standard, socket and file descriptors.

SPIFFS_FILEHDL_OFFSET was updated accordingly but the code didn't use
that constant and this broke the SPIFFS POSIX API.

Fix it by initializing the fh_ix_offset field of the spiffs_config
structure to SPIFFS_FILEHDL_OFFSET.

Zaltora/esp-open-rtos,ourairquality/esp-open-rtos,bhuvanchandra/esp-open-rtos,SuperHouse/esp-open-rtos,ourairquality/esp-open-rtos,SuperHouse/esp-open-rtos,UncleRus/esp-open-rtos,bhuvanchandra/esp-open-rtos,bhuvanchandra/esp-open-rtos,UncleRus/esp-open-rtos,ourairquality/esp-open-rtos,UncleRus/esp-open-rtos,UncleRus/esp-open-rtos,urx/esp-open-rtos,Zaltora/esp-open-rtos,SuperHouse/esp-open-rtos,Zaltora/esp-open-rtos,urx/esp-open-rtos,ourairquality/esp-open-rtos,bhuvanchandra/esp-open-rtos,UncleRus/esp-open-rtos,urx/esp-open-rtos,SuperHouse/esp-open-rtos,urx/esp-open-rtos,ourairquality/esp-open-rtos,Zaltora/esp-open-rtos,urx/esp-open-rtos,Zaltora/esp-open-rtos,urx/esp-open-rtos,ourairquality/esp-open-rtos,Zaltora/esp-open-rtos,SuperHouse/esp-open-rtos,UncleRus/esp-open-rtos,SuperHouse/esp-open-rtos