[sw, dif] Fix spelling of 'occurred' in all DIFs and template

Signed-off-by: Michael Munday <mike.munday@lowrisc.org>
diff --git a/sw/device/lib/dif/dif_alert_handler.h b/sw/device/lib/dif/dif_alert_handler.h
index a37c9b6..3cec0a9 100644
--- a/sw/device/lib/dif/dif_alert_handler.h
+++ b/sw/device/lib/dif/dif_alert_handler.h
@@ -90,7 +90,7 @@
    * Indicates that some parameter passed into a function failed a
    * precondition.
    *
-   * When this value is returned, no hardware operations occured.
+   * When this value is returned, no hardware operations occurred.
    */
   kDifAlertHandlerBadArg = 2,
 } dif_alert_handler_result_t;
@@ -111,7 +111,7 @@
    * Indicates that some parameter passed into a function failed a
    * precondition.
    *
-   * When this value is returned, no hardware operations occured.
+   * When this value is returned, no hardware operations occurred.
    */
   kDifAlertHandlerConfigBadArg = kDifAlertHandlerBadArg,
   /**