kqueue: fix conversion of timer data to sbintime

This unbreaks the i386 kqueue timer tests after a recent change switched
NOTE_ABSTIME over to using microseconds. Notably, the data argument (which
holds useconds) is an int64_t, but we were passing it to timer2sbintime
which takes an intptr_t. Perhaps in a previous incarnation, intptr_t would
have made sense, but now it just leads to the timestamp getting truncated
and subsequently rejected when it no longer fits in an intptr_t.

PR:		245768
Reported by:	lwhsu / CI
MFC after:	1 week

sys/kern/kern_event.c

@@ -619,7 +619,7 @@ knote_fork(struct knlist *list, int pid)
     (NOTE_SECONDS | NOTE_MSECONDS | NOTE_USECONDS | NOTE_NSECONDS)
 
 static sbintime_t
-timer2sbintime(intptr_t data, int flags)
+timer2sbintime(int64_t data, int flags)
 {
 	int64_t secs;