ACPICA: Debug output: Do not emit function nesting level for kernel build.

The nesting level is really only useful during a single-thread
execution. Therefore, only enable this output for the AcpiExec
utility. Also, only emit the thread ID when executing under AcpiExec.
(Context switches are still detected and a message is emitted.)
ACPICA BZ 972.

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