as: fix antic_expire check

Fix units mismatch (jiffies vs msecs) in as-iosched.c, spotted by Xiaoning
Ding <dingxn@cse.ohio-state.edu>.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>