Shifted block_recycles so 0 => pure copy-on-write

This makes a bit more sense with the new block_recycles name.
block_recycles=0 (previously block_recycles=1) requires 1 erase, but it
doesn't really "recycle" the block. With this change, block_recycles=1
"recycles" the block once (2 erases in total) before relocating, which I
think is a bit more intuitive.

Note, this sort of messes with our power-of-2 rounding, as the
block_recycles is technically rounded down to the nearest power-of-2
after adding 1:

- block_recycles=1022 -> 512 erases
- block_recycles=1023 -> 1024 erases
- block_recycles=1024 -> 1024 erases
- block_recycles=1025 -> 1024 erases

But I'm going to keep the block_recycles description more-or-less as is
for now, as I think this extra detail is more confusing than useful,
powers-of-2 stay powers-of-2, and the <=block_recycles contraint is not
violated.

lfs.c

@@ -15286,9 +15286,6 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
 //    // wear-leveling.
 //    LFS_ASSERT(lfs->cfg->block_cycles != 0);
 
-    // block_recycles should not be zero, use -1 to disable
-    LFS_ASSERT(lfs->cfg->block_recycles != 0);
-
     // inline_size must be <= block_size/4
     LFS_ASSERT(lfs->cfg->inline_size <= lfs->cfg->block_size/4);
     // shrub_size must be <= block_size/4
@@ -15375,12 +15372,13 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
 
     // find the number of bits to use for recycle counters
     //
-    // Multiply by 2, since we alternate which metadata block we erase each
-    // compaction, and limit to 28-bits so we always have some bits to
-    // determine the most recent revision.
+    // Add 1, to include the initial erase, multiply by 2, since we
+    // alternate which metadata block we erase each compaction, and limit
+    // to 28-bits so we always have some bits to determine the most recent
+    // revision.
     if (lfs->cfg->block_recycles != -1) {
         lfs->recycle_bits = lfs_min(
-                lfs_nlog2(2*lfs->cfg->block_recycles+1)-1,
+                lfs_nlog2(2*(lfs->cfg->block_recycles+1)+1)-1,
                 28);
     } else {
         lfs->recycle_bits = -1;