Fixes another (smaller) race condition in ESP32's select wakeup.

The wakeup_from_isr routine consults the pendingWakeup_ and inSelect_ variables.
These variables need to be locked, because multi-core ESP32's could run an isr
on one core and othercode on a different core.

Moves the atomic lock from esp_wakeup_from_isr into OSSelectWakeup::wakeup_from_isr.

src/os/OSSelectWakeup.cxx

@@ -240,7 +240,6 @@ void OSSelectWakeup::esp_wakeup()
 /// call from within an ISR context.
 void OSSelectWakeup::esp_wakeup_from_isr()
 {
-    AtomicHolder h(this);
     BaseType_t woken = pdFALSE;
 
     // If our VFS FD is not set in the except fd_set we can exit early.

src/os/OSSelectWakeup.hxx

@@ -159,6 +159,10 @@ public:
 #if OPENMRN_FEATURE_RTOS_FROM_ISR
     void wakeup_from_isr()
     {
+#if defined(ESP_PLATFORM)
+        // On multi-core ESP32s we need to lock objects even in ISRs.
+        AtomicHolder h(this);
+#endif
         pendingWakeup_ = true;
         if (inSelect_)
         {