perf script: Kill script_spec__delete

As script_spec__delete() frees given struct script_spec it should not be
called if we failed to allocate the struct. Also it's the only caller of
the function, we can get rid of the function itself.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1325000151-4463-4-git-send-email-namhyung@gmail.com
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>