x86: Clean up mtrr/amd.c:

Fix trivial style problems :

  ERROR: trailing whitespace
  WARNING: line over 80 characters
  ERROR: do not use C99 // comments

arch/x86/kernel/cpu/mtrr/amd.o:

   text	   data	    bss	    dec	    hex	filename
    501	     32	      0	    533	    215	amd.o.before
    501	     32	      0	    533	    215	amd.o.after

md5:
   62f795eb840ee2d17b03df89e789e76c  amd.o.before.asm
   62f795eb840ee2d17b03df89e789e76c  amd.o.after.asm

Suggested-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <20090703164225.GA21447@elte.hu>
[ Also restructured comments to be standard, removed stray return,
  converted function description to DocBook style, etc. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>