perf probe: Fix examples section of documentation

perf probe: Fix examples section of documentation

An example in perf-probe documentation for pattern of function name
based probe addition is not providing example command for that case.

This commit fixes the example to give appropriate example command.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Taeung Song <treeze.taeung@gmail.com>
Fixes: 7bb3af1d56a5 ("perf probe: Update perf probe document")
Link: http://lkml.kernel.org/r/20170507103642.30560-1-sj38.park@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>