perf probe: Fix to show correct error string

perf probe: Fix to show correct error string

commit 44a56040a0037a845d5fa218dffde464579f0cab upstream.

Fix perf probe to show correct error string when it
fails to delete an event. The write(2) returns -1
if failed, and errno stores real error number.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Link: http://lkml.kernel.org/r/20111004104504.14591.41266.stgit@fedora15
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>