compare with jiffies

Most of time_after like macros usages just compare jiffies and another number,
so here add some time_is_* macros for convenience.

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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