ACPI: Remove assorted unused declarations of functions

acpi_create_dir()/acpi_remove_dir() are never implemented since
the beginning of git history.

Commit f8d31489 ("ACPICA: Debugger: Convert some mechanisms to OSPM specific")
declared but never implemented acpi_run_debugger().

Commit 781d737c ("ACPI: Drop power resources driver")
removed acpi_power_init() but not its declaration.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>