ACPICA: Namespace: Rename acpi_gbl_reg_methods_enabled to acpi_gbl_namespace_initialized

ACPICA commit 4be3b82cf45d324366ea8567102d5108c5ef47cb
ACPICA commit 19f84c249267fab0bfb138bd14d12510fb4faf24

The global variable actually means the availability of the namespace, and
control methods evaluations should happen after namespace readiness. Thus
this patch renames the global variable to reflect this logic. Lv Zheng.

Link: https://github.com/acpica/acpica/commit/4be3b82c
Link: https://github.com/acpica/acpica/commit/19f84c24


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>