Staging: lustre: ptlrpc: pinger: Declare as static

Declare ptlrpc_pinger_remove_timeouts as static since it is used
only in this particular file.

Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>