timer/timer_getoverrun: adjust the default errno from ENOSYS to EINVAL

modify the default errno from ENOSYS to EINVAL can pass the ltp
case: ltp_timer_getoverrun_speculative_6_1,
ltp_timer_getoverrun_speculative_6_2, ltp_timer_getoverrun_speculative_6_3

Signed-off-by: guoshichao <guoshichao@xiaomi.com>

sched/timer/timer_getoverrun.c

@@ -76,7 +76,7 @@
 int timer_getoverrun(timer_t timerid)
 {
   UNUSED(timerid);
-  set_errno(ENOSYS);
+  set_errno(EINVAL);
   return ERROR;
 }