sched: Force sched_try_shutdown to be inlined

If sched_try_shutdown() is not inlined into timer_dispatch_many() it
can have a significant impact on benchmarks.  (Even though the
function isn't called in practice, the call causes gcc to organize the
function differently.)

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/sched.c

@@ -304,7 +304,7 @@ sched_report_shutdown(void)
 }
 
 // Shutdown the machine if not already in the process of shutting down
-void
+void __always_inline
 sched_try_shutdown(uint_fast8_t reason)
 {
     if (!shutdown_status)