qemu-timer: drop outdated signal safety comments

host_alarm_handler() is invoked from the signal processing thread
(currently the iothread).  Previously we did processing in a real signal
handler with signalfd and therefore needed signal-safe timer code.

Today host_alarm_handler() just marks the alarm timer as expired/pending
and notifies the main loop using qemu_notify_event().

Therefore these outdated comments about signal safety can be dropped.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

qemu-timer.c

@@ -301,8 +301,6 @@ void timer_del(QEMUTimer *ts)
 {
     QEMUTimer **pt, *t;
 
-    /* NOTE: this code must be signal safe because
-       timer_expired() can be called from a signal. */
     pt = &ts->timer_list->active_timers;
     for(;;) {
         t = *pt;
@@ -325,8 +323,6 @@ void timer_mod_ns(QEMUTimer *ts, int64_t expire_time)
     timer_del(ts);
 
     /* add the timer in the sorted list */
-    /* NOTE: this code must be signal safe because
-       timer_expired() can be called from a signal. */
     pt = &ts->timer_list->active_timers;
     for(;;) {
         t = *pt;