coresight: Fix uninitialised pointer bug in etm_setup_aux()

coresight: Fix uninitialised pointer bug in etm_setup_aux()

Commit [bb1860efc817] changed the sink handling code introducing an
uninitialised pointer bug. This results in the default sink selection
failing.

Prior to commit:

static void etm_setup_aux(...)

<snip>
        struct coresight_device *sink;
<snip>

        /* First get the selected sink from user space. */
        if (event->attr.config2) {
                id = (u32)event->attr.config2;
                sink = coresight_get_sink_by_id(id);
        } else {
                sink = coresight_get_enabled_sink(true);
        }
<ctd>

*sink always initialised - possibly to NULL which triggers the
automatic sink selection.

After commit:

static void etm_setup_aux(...)

<snip>
        struct coresight_device *sink;
<snip>

        /* First get the selected sink from user space. */
        if (event->attr.config2) {
                id = (u32)event->attr.config2;
                sink = coresight_get_sink_by_id(id);
        }
<ctd>

*sink pointer uninitialised when not providing a sink on the perf command
line. This breaks later checks to enable automatic sink selection.

Fixes: bb1860efc817 ("coresight: etm: perf: Sink selection using sysfs is deprecated")
Signed-off-by: Mike Leach <[email protected]>
Signed-off-by: Mathieu Poirier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>