x86, ioremap: Fix normal ram range check

Check for normal RAM in x86 ioremap() code seems to not work for the
last page frame in the specified physical address range.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
LKML-Reference: <4C1AE6CD.1080704@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>