In the TUI the 's' hotkey can be used to switch to another perf.data
file in the current directory, but that got broken in Fixes:
b01141f4 ("perf annotate: Initialize the priv are in symbol__new()"),
that would show this once another file was chosen:

    ┌─Fatal Error─────────────────────────────────────┐
    │Annotation needs to be init before symbol__init()│
    │                                                 │
    │                                                 │
    │Press any key...                                 │
    └─────────────────────────────────────────────────┘

Fix it by just silently bailing out if symbol__annotation_init() was already
called, just like is done with symbol__init(), i.e. they are done just once at
session start, not when switching to a new perf.data file.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Martin Liška <mliska@suse.cz>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: b01141f4 ("perf annotate: Initialize the priv are in symbol__new()")
Link: https://lkml.kernel.org/n/tip-ogppdtpzfax7y1h6gjdv5s6u@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>