AP_HAL_QURT: Scheduler: replace use of in_timerprocess()

This function actually checks if we are not in the main thread rather
than if we are in the timer thread.

Add a new function that does what it's supposed to do.

libraries/AP_HAL_QURT/Scheduler.cpp

@@ -70,7 +70,7 @@ void Scheduler::delay_microseconds(uint16_t usec)
 
 void Scheduler::delay(uint16_t ms)
 {
-    if (in_timerprocess()) {
+    if (!in_main_thread()) {
         ::printf("ERROR: delay() from timer process\n");
         return;
     }
@@ -266,6 +266,11 @@ bool Scheduler::in_timerprocess()
     return getpid() != _main_task_pid;
 }
 
+bool Scheduler::in_main_thread()
+{
+    return getpid() == _main_task_pid;
+}
+
 void Scheduler::system_initialized() {
     if (_initialized) {
         AP_HAL::panic("PANIC: scheduler::system_initialized called"

libraries/AP_HAL_QURT/Scheduler.h

@@ -31,6 +31,7 @@ public:
     void     resume_timer_procs();
     void     reboot(bool hold_in_bootloader);
 
+    bool     in_main_thread();
     bool     in_timerprocess();
     void     system_initialized();
     void     hal_initialized();