Random NVS fixes

* Checking Lock::init() now
* fixed typos in nvs_flash.h
* Added missing parameter checks in nvs encryption
  function

* Closes IDF-1462
* Closes IDF-2900

components/nvs_flash/src/nvs_handle_locked.cpp

@@ -15,9 +15,7 @@
 
 namespace nvs {
 
-NVSHandleLocked::NVSHandleLocked(NVSHandleSimple *handle) : handle(handle) {
-    Lock::init();
-}
+NVSHandleLocked::NVSHandleLocked(NVSHandleSimple *handle) : handle(handle) { }
 
 NVSHandleLocked::~NVSHandleLocked() {
     Lock lock;