Use USEC_PER_SEC instead of 1000000, that making the later bugfix
more clearly.
Signed-off-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>