x86: Move range related operation to one file

We have almost the same code for mtrr cleanup and amd_bus checkup, and
this code  will also be used in replacing bootmem with early_res,
so try to move them together and reuse it from different parts.

Also rename update_range to subtract_range as that is what the
function is actually doing.

-v2: update comments as Christoph requested

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <1265793639-15071-4-git-send-email-yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/kernel/Makefile b/kernel/Makefile
index 864ff75..ad47330 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@
 	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
 	    hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
 	    notifier.o ksysfs.o pm_qos_params.o sched_clock.o cred.o \
-	    async.o
+	    async.o range.o
 obj-y += groups.o
 
 ifdef CONFIG_FUNCTION_TRACER