[S390] __div64_32 for 31 bit.
The clocksource infrastructure introduced with commit ad596171 broke 31 bit s390. The reason is that the do_div() primitive for 31 bit always had a restriction: it could only divide an unsigned 64 bit integer by an unsigned 31 bit integer. The clocksource code now uses do_div() with a base value that has the most significant bit set. The result is that clock->cycle_interval has a funny value which causes the linux time to jump around like mad. The solution is "obvious": implement a proper __div64_32 function for 31 bit s390. Signed-off-by: Martin Schwidefsky <email@example.com>