ACPICA: Remove acpi_gbl_group_module_level_code and only use acpi_gbl_execute_tables_as_methods instead

acpi_gbl_group_module_level_code and acpi_gbl_execute_tables_as_methods were
used to enable different table load behavior. The different table
load behaviors are as follows:

A.) acpi_gbl_group_module_level_code enabled the legacy approach where
    ASL if statements are executed after the namespace object has
    been loaded.
B.) acpi_gbl_execute_tables_as_methods is currently used to enable the
    table load to be a method invocation. This meaning that ASL If
    statements are executed in-line rather than deferred until after
    the ACPI namespace has been populated. This is the correct
    behavior and option A will be removed in the future.

We do not support a table load behavior where these variables are
assigned the same value. In otherwords, we only support option A or B
and do not need acpi_gbl_group_module_level_code to enable A. From now on,
acpi_gbl_execute_tables_as_methods == 0 enables option A and
acpi_gbl_execute_tables_as_methods == 1 enables option B.

Note: option A is expected to be removed in the future and option B
will become the only supported table load behavior.
Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>