Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/fs/logfs/dev_mtd.c b/fs/logfs/dev_mtd.c
index 7466e9d..339e17e 100644
--- a/fs/logfs/dev_mtd.c
+++ b/fs/logfs/dev_mtd.c
@@ -60,7 +60,7 @@
  * asynchronous properties.  So just to prevent the first implementor of such
  * a thing from breaking logfs in 2350, we do the usual pointless dance to
  * declare a completion variable and wait for completion before returning
- * from mtd_erase().  What an excercise in futility!
+ * from mtd_erase().  What an exercise in futility!
  */
 static void logfs_erase_callback(struct erase_info *ei)
 {