ACPICA: acpidump: Update MAINTAINERS file to include tools folder for ACPI/ACPICA.

This patch updates MAINTAINERS file, adding tools/power/acpi for ACPI and
ACPICA.

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