ACPI / OSL: Add support to install tables via initrd

This patch adds support to install tables from initrd.

If a table in the initrd wasn't used by the override mechanism,
the table would be installed after initializing all RSDT/XSDT
tables.

Link: https://lkml.org/lkml/2014/2/28/368
Reported-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>