perf probe: Print debug messages using pr_*()

Use the new pr_{err,warning,debug,etc} printout methods, just
like in the kernel.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1256153646-10097-1-git-send-email-acme@redhat.com>
[ Split this patch out, to keep perf/probes separate. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>