Remove setup_kfail server/13796 in disp-step-syscall.exp

Remove setup_kfail server/13796 in disp-step-syscall.exp

This patch series add fork support in target remote,

  [PATCH v2 0/3] Target remote mode fork and exec support
  https://sourceware.org/ml/gdb-patches/2015-12/msg00144.html

so GDB can be informed about the child, and adjust child correctly in
displaced stepping.  The PR server/13796 was fixed by this patch
series actually.  Test results on buildbot show this KFAIL->KPASS
change https://sourceware.org/ml/gdb-testers/2015-q4/msg10128.html

gdb/testsuite:

2016-02-18  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/disp-step-syscall.exp (disp_step_cross_syscall):
	Don't call setup_kfail.