delay loops in i386 BSPs

[Ian Lance Taylor <ian@zembu.com>]

Does anybody have any code for properly calibrated delay loops in the
i386 BSPs?

Most of the BSPs have a simple minded delay macro, which is incorrect
on most machines.

The code in pc386/timer/timer.c calibrates a timer, but unfortunately
only calibrates for milliseconds.  Most drivers need microsecond
delays.

Ian