The real difference between the mmu and non-mmu varients of the delay.h
files has nothing to do with having an mmu or not. It is processor family
differences that means slightly different code. Merge the delay_mm.h and
delay_no.h files back into a single file.

The primarly difference we need to deal with is whether the processor
supports a 32bit * 32bit -> 64bit multiply. Without it we need to do some
shift scaling as well as use a 32bit * 32bit -> 32bit multiply. If building
for a multi-CPU type kernel then we must use the simpler mult/shift scaling.

This version of delay code allows the CPU32 family to use a 64bit mul,
since it supports this instruction, the old code did not.

The changes use macros where appropriate to try and optimize constant sized
udelay times. And it removes the use of a fixed lib function for the non-mmu
case. Code size on typical kernel configurations is similar, or only larger
by a few tens of bytes.

Also removed the unused muldiv() code from delay_mm.h.

Build and run tested on ColdFire and ARAnyM. Build tested only on 68328
and 68360 (CPU32).
Signed-off-by: Greg Ungerer <gerg@uclinux.org>