ACPICA: Debugger: Split debugger initialization/termination APIs

ACPICA commit 7a3f22baab000b186779dac64ad71d9776b8f432

It is likely that the debugger is enabled only when a userspace program
explicitly tells a kernel to do so, so it shouldn't be initialized as
early as current implementation.

The only tool requiring ACPI_DEBUGGER is acpiexec, so acpiexec need to call
the new APIs by itself. And BSD developers may also get notified to invoke
the APIs for DDB enabling. Lv Zheng.

This patch doesn't affect Linux kernel as debugger is currently not enabled
in the Linux kernel.

Link: https://github.com/acpica/acpica/commit/7a3f22ba


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>