Redo of PR#5345. Fixed spelling and typographical errors found by CodeSpell.

Signed-off-by: Shaun Case <warmsocks@gmail.com>
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/include/mbedtls/debug.h b/include/mbedtls/debug.h
index 0aed596..5c8aba8 100644
--- a/include/mbedtls/debug.h
+++ b/include/mbedtls/debug.h
@@ -139,7 +139,7 @@
  *          discarded.
  *          (Default value: 0 = No debug )
  *
- * \param threshold     theshold level of messages to filter on. Messages at a
+ * \param threshold     threshold level of messages to filter on. Messages at a
  *                      higher level will be discarded.
  *                          - Debug levels
  *                              - 0 No debug