fs: littlefs: Rename *area (struct flash_area*) to *backend void pointer

The struct flash_area *area pointer has been renamed to void *backend
pointer.

This change is enabling further rework of the littlefs subsystem to work
with other backend devices (like block ones - i.e. SD card).

Signed-off-by: Lukasz Majewski <lukma@denx.de>
2 files changed