ACPI / osi: Cleanup OSI handling code to use bool

This patch changes "int/unsigned int" to "bool" to simplify the code.

Tested-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>