perf annotate: Create a annotate2 flag in struct symbol

We often use the symbol__annotate2() to annotate a specified symbol.
While annotating may take some time, so in order to avoid annotating the
same symbol repeatedly, the patch creates a new flag to indicate the
symbol has been annotated.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1543586097-27632-3-git-send-email-yao.jin@linux.intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>