lfs: correct documentation on lookahead-related values
lfs: correct documentation on lookahead-related values

The size of the lookahead buffer is required to be a multiple of 8 bytes
in anticipation of a future improvement.  The buffer itself need only be
aligned to support access through a uint32_t pointer.

Signed-off-by: Peter A. Bigot <650538893330be855f76604594b4820eb226769e@pabigot.com>

geky/littlefs,geky/littlefs,geky/littlefs,geky/littlefs,littlefs-project/littlefs,littlefs-project/littlefs