core: fix bug in gettimeofday

gettimeofday used to return timestamps which had tv_sec 1000 times smaller than the correct value.
s_bootTime is in seconds, so no need to divide it by 1000.

Author: igrr

cores/esp8266/time.c

@@ -97,7 +97,7 @@ int _gettimeofday_r(struct _reent* unused, struct timeval *tp, void *tzp)
     if (tp)
     {
         ensureBootTimeIsSet();
-        tp->tv_sec  = (s_bootTime + millis()) / 1000;
+        tp->tv_sec  = s_bootTime + millis() / 1000;
         tp->tv_usec = micros() * 1000;
     }
     return 0;