Fixed assert with branches in lfs3_file_traverse_

This was modified incorrectly for LFS3_2BONLY. We do actually end up
with non-bptr non-data tags here when we encounter btree inner nodes.

Code changes:

           code          stack          ctx
  before: 37864           2416          636
  after:  37888 (+0.1%)   2416 (+0.0%)  636 (+0.0%)

Author: geky

lfs3.c

@@ -14208,9 +14208,7 @@ static int lfs3_file_traverse_(lfs3_t *lfs3, const lfs3_bshrub_t *bshrub,
     }
 
     // decode bptrs
-    if (tag == LFS3_TAG_DATA) {
-        bptr->data = data;
-    } else if (LFS3_IFDEF_2BONLY(false, tag == LFS3_TAG_BLOCK)) {
+    if (LFS3_IFDEF_2BONLY(false, tag == LFS3_TAG_BLOCK)) {
         #ifndef LFS3_2BONLY
         err = lfs3_data_readbptr(lfs3, &data,
                 bptr);
@@ -14219,7 +14217,7 @@ static int lfs3_file_traverse_(lfs3_t *lfs3, const lfs3_bshrub_t *bshrub,
         }
         #endif
     } else {
-        LFS3_UNREACHABLE();
+        bptr->data = data;
     }
 
     if (tag_) {