x86/tools: Fix insn_sanity message outputs

Fix x86 instruction decoder test to dump all error messages
to stderr and others to stdout.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: yrl.pp-manager.tt@hitachi.com
Link: http://lkml.kernel.org/r/20111205120550.15475.70149.stgit@cloud


Signed-off-by: Ingo Molnar <mingo@elte.hu>