x86: apic: Fixmap apic address even if apic disabled

In case if apic were disabled by boot option
we still need read_apic operation. So fixmap
a fake apic area if needed.

[ Impact: fix boot crash ]

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: yinghai@kernel.org
Cc: eswierk@aristanetworks.com
LKML-Reference: <20090511134140.GH4624@lenovo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>