Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 58250e0..199a801 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2346,7 +2346,7 @@
 		root = next->root;
 		BUG_ON(!root);
 
-		/* no other choice for non-refernce counted tree */
+		/* no other choice for non-references counted tree */
 		if (!root->ref_cows)
 			return root;