arch/alpha/kernel/traps.c: use time_* macros

The functions time_before, time_before_eq, time_after, and time_after_eq are
more robust for comparing jiffies against other values.

So implement usage of the time_after() macro, defined in linux/jiffies.h,
which deals with wrapping correctly

[akpm@linux-foundation.org: fix warning]
Signed-off-by: S.Caglar Onur <caglar@pardus.org.tr>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>