perf ui/tui: Protect windows by ui__lock

Sometimes perf top TUI breaks display with concurrent help/input window
and pr_* messages since they're not protected by ui__lock.

You can check it by pressing (and not releasing) 'h' key on a "perf top
-vvv" TUI session.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1388036284-32342-2-git-send-email-namhyung@kernel.org


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