Fix warning in gdb.base/signals-state-child.c

Fix warning in gdb.base/signals-state-child.c

I see the following warning when running signals-state-child.exp.

gdb/testsuite/gdb.base/signals-state-child.c:77:4: warning: too many arguments for format [-Wformat-extra-args]
    fprintf (out, "sigaction={sa_handler=", i);
    ^

this patch is to remove the argument from fprintf.

gdb/testsuite:

2016-08-12  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/signals-state-child.c (main): Remove "i" from fprintf's
	argument list.