perf probe: Cleanup debuginfo related code

Cleanup debuginfo related code to eliminate fragile code which
pointed by Ingo (Thanks!).
1) Invert logic of NO_DWARF_SUPPORT to DWARF_SUPPORT.
2) For removing assymetric/local variable ifdefs, introduce
  more helper functions.
3) Change options order to reduce the number of ifdefs.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1269274229-20442-2-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>