Reverted lfsr_data_t lazily encoded leb128s

- It didn't save code.

- An inlined buffer is potentially more useful, even if only marginally,
  and, uh, unproven yet.

- Requiring lfs_toleb128 in a readonly implementation is a hard ask.

lfs_util.h

@@ -348,11 +348,6 @@ ssize_t lfs_toleb128(uint32_t word, void *buffer, size_t size);
 
 ssize_t lfs_fromleb128(uint32_t *word, const void *buffer, size_t size);
 
-// Calculate the on-disk size of a leb128 without actually encoding
-static inline size_t lfs_sizeleb128(uint32_t word) {
-    return (lfs_nlog2(word+1)+7-1) / 7;
-}
-
 
 
 // Calculate CRC-32 with polynomial = 0x04c11db7