ACPICA: Deploy ACPI_EXPORT_SYMBOL_INIT for main ACPICA initialization interfaces.

This changes can reduce source code differences between Linux and ACPICA
upstream to help improving the release automation.

The side effect of applying this patch in Linux is:
1. Some ACPICA initialization/termination APIs are no longer exported in
   Linux, these include:
    acpi_load_tables
    acpi_initialize_subsystem
    acpi_enable_subsystem
    acpi_initialize_objects
    acpi_terminate
2. This patch does not affect the following APIs as they are currently not
   marked with ACPI_EXPORT_SYMBOL in Linux:
    acpi_reallocate_root_table
    acpi_initialize_tables
Such functions should not be exported as they are internal to ACPI
subsystem in Linux, and will only be invoked inside of ACPI subsystem's
initialization routines marked with __init and termination routines marked
with __exit.  While on other OSPMs, such functions may still need to be
exported.

Thus this patch adds the configurability for ACPICA, so that it leaves
OSPMs to determine if the __init/__exit marked functions should be exported
or not.  Lv Zheng.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>