perf annotate TUI browser: Do not use member from variable within its own initialization

perf annotate TUI browser: Do not use member from variable within its own initialization

Some compilers will complain when using a member of a struct to
initialize another member, in the same struct initialization.

For instance:

  debian:8      Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)
  oraclelinux:7 clang version 3.4.2 (tags/RELEASE_34/dot2-final)

Produce:

  ui/browsers/annotate.c:104:12: error: variable 'ops' is uninitialized when used within its own initialization [-Werror,-Wuninitialized]
                                              (!ops.current_entry ||
                                                ^~~
  1 error generated.

So use an extra variable, initialized just before that struct, to have
the value used in the expressions used to init two of the struct
members.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Fixes: c298304bd747 ("perf annotate: Use a ops table for annotation_line__write()")
Link: https://lkml.kernel.org/n/tip-f9nexro58q62l3o9hez8hr0i@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>