perf probe: Fix !dwarf build

perf probe: Fix !dwarf build

Fix the !drawf build.

This uses the existing NO_DWARF_SUPPORT mechanism we use for that,
but it's really fragile and needs a cleanup. (in a separate patch)

1) Such uses:

 #ifndef NO_DWARF_SUPPORT

are double inverted logic a'la 'not not'. Instead the flag should
be called DWARF_SUPPORT.

2) Furthermore, assymetric #ifdef polluted code flow like:

        if (need_dwarf)
 #ifdef NO_DWARF_SUPPORT
                die("Debuginfo-analysis is not supported");
 #else   /* !NO_DWARF_SUPPORT */
                pr_debug("Some probes require debuginfo.\n");

        fd = open_vmlinux();

is very fragile and not acceptable. Instead of that helper functions
should be created and the dwarf/no-dwarf logic should be separated more
cleanly.

3) Local variable #ifdefs like this:

 #ifndef NO_DWARF_SUPPORT
        int fd;
 #endif

Are fragile as well and should be eliminated. Helper functions achieve
that too.

Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100316220612.32050.33806.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>