Currently we have a confused udelay implementation.

* __const_udelay does not accept usecs but xloops in i386 and x86_64
* our implementation requires usecs as arg
* it gets a xloops count when called by asm/arch/delay.h

Bugs related to this (extremely long shutdown times) where reported by some
x86_64 users, especially using Device Mapper.

To hit this bug, a compile-time constant time parameter must be passed -
that's why UML seems to work most times.  Fix this with a simple udelay
implementation.
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: NJeff Dike <jdike@addtoit.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>