plugin:python: fix compiler warning

The function `load_plugin` is passed, as argument, to
`trace_util_load_plugins()` but the prototype was not exactly the same.

Link: http://lkml.kernel.org/r/20170423102258.21609-2-federico.vaga@vaga.pv.it

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
1 file changed