checkpatch: warn on comparisons to get_jiffies_64()

Comparing get_jiffies_64() is almost always wrong and time_before64 and
time_after64 should be used instead.

Warn on any comparison to get_jiffies_64().

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>