Don't skip catch-syscall.exp on hppa*-hp-hpux* target

Don't skip catch-syscall.exp on hppa*-hp-hpux* target

As far as I know, "catch syscall" is supported on hppa*-hp-hpux*, but
the test catch-syscall.exp is skipped on this target by mistake.  This
patch is to fix it.  However, I don't have a hpux machine to test.

gdb/testsuite:

2015-02-27  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/catch-syscall.exp: Don't skip it on hppa*-hp-hpux*
	target.