HPET: fix ACPI memory range length handling

ACPI address space descriptors contain _MIN, _MAX, and _LEN.  _MIN and _MAX
are the bounds within which the region can be moved (this is clarified in
Table 6-38 of the ACPI 3.0 spec).  We should use _LEN to determine the size
of the region, not _MAX - _MIN + 1.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/char/hpet.c

@@ -925,11 +925,8 @@ static acpi_status hpet_resources(struct acpi_resource *res, void *data)
 	status = acpi_resource_to_address64(res, &addr);
 
 	if (ACPI_SUCCESS(status)) {
-		unsigned long size;
-
-		size = addr.maximum - addr.minimum + 1;
 		hdp->hd_phys_address = addr.minimum;
-		hdp->hd_address = ioremap(addr.minimum, size);
+		hdp->hd_address = ioremap(addr.minimum, addr.address_length);
 
 		if (hpet_is_known(hdp)) {
 			printk(KERN_DEBUG "%s: 0x%lx is busy\n",