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 <pab@pabigot.com>

lfs.h

@@ -204,7 +204,7 @@ struct lfs_config {
     // Size of the lookahead buffer in bytes. A larger lookahead buffer
     // increases the number of blocks found during an allocation pass. The
     // lookahead buffer is stored as a compact bitmap, so each byte of RAM
-    // can track 8 blocks. Must be a multiple of 4.
+    // can track 8 blocks. Must be a multiple of 8.
     lfs_size_t lookahead_size;
 
     // Optional statically allocated read buffer. Must be cache_size.
@@ -216,7 +216,7 @@ struct lfs_config {
     void *prog_buffer;
 
     // Optional statically allocated lookahead buffer. Must be lookahead_size
-    // and aligned to a 64-bit boundary. By default lfs_malloc is used to
+    // and aligned to a 32-bit boundary. By default lfs_malloc is used to
     // allocate this buffer.
     void *lookahead_buffer;