lttng-{enable-event(1),event-rule(7)}: `--filter` is not always avail.

lttng-{enable-event(1),event-rule(7)}: `--filter` is not always avail.

The `--filter` option of both lttng-enable-event(1) and a common event
rule specification is not available with the Linux kprobe, kretprobe,
and user space probe instrumentation point types.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I2cea488359bbe8ac8494d785fe3282419ee66d46