o Randy Dunlap reported following linux-next failure. This patch fixes it.
on i386:
blk-throttle.c:(.text+0x1abb8): undefined reference to `__udivdi3'
blk-throttle.c:(.text+0x1b1dc): undefined reference to `__udivdi3'
o bytes_per_second interface is 64bit and I was continuing to do 64 bit
division even on 32bit platform without help of special macros/functions
hence the failure.