ACPI: Document ACPI table overriding via initrd

Signed-off-by: Thomas Renninger <trenn@suse.de>
Link: http://lkml.kernel.org/r/1349043837-22659-7-git-send-email-trenn@suse.de


Cc: Len Brown <lenb@kernel.org>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>