ACPICA: Common: Enhance acpi_getopt() to improve portability

This patch enhances acpi_getopt() by converting the standard C library
invocations into portable ACPI string APIs and acpi_log_error() to improve
portability. Lv Zheng.

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>