AP_HAL: Remove timer process suspension interface

libraries/AP_HAL/Scheduler.h

@@ -49,10 +49,6 @@ public:
     // register a low priority IO task
     virtual void     register_io_process(AP_HAL::MemberProc) = 0;
 
-    // suspend and resume both timer and IO processes
-    virtual void     suspend_timer_procs() = 0;
-    virtual void     resume_timer_procs() = 0;
-
     virtual void     register_timer_failsafe(AP_HAL::Proc,
                                              uint32_t period_us) = 0;