perf annotate: Fix objdump --no-show-raw-insn flag

perf annotate: Fix objdump --no-show-raw-insn flag

Remove redirection of objdump's stderr to /dev/null to help diagnose
failures.

Fix the '--no-show-raw' flag to be '--no-show-raw-insn' which binutils
is permissive and allows, but fails with LLVM objdump.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: clang-built-linux@googlegroups.com
Link: http://lore.kernel.org/lkml/20191010183649.23768-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>