Call enqueue_pending_signal in linux_resume_one_lwp_throw

Replace the code which is exactly what enqueue_pending_signal does.

gdb/gdbserver:

2016-03-02  Yao Qi  <yao.qi@linaro.org>

	* linux-low.c (linux_resume_one_lwp_throw): Replace code with
	enqueue_pending_signal.