Upstream: zil_commit_waiter() can stall forever

On macOS clock_t is unsigned, so when cv_timedwait_hires() returns -1
we loop forever. The conditional was tweaked to ignore signedness.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Jorgen Lundman <lundman@lundman.net>
Closes openzfs#10445

module/zfs/zil.c

@@ -2691,7 +2691,7 @@ zil_commit_waiter(zilog_t *zilog, zil_commit_waiter_t *zcw)
 			    &zcw->zcw_lock, wakeup, USEC2NSEC(1),
 			    CALLOUT_FLAG_ABSOLUTE);
 
-			if (timeleft >= 0 || zcw->zcw_done)
+			if (timeleft != -1 || zcw->zcw_done)
 				continue;
 
 			timedout = B_TRUE;