intel_th: gth: Fix an off-by-one in output unassigning

BugLink: https://bugs.launchpad.net/bugs/1830176

commit 91d3f8a6 upstream.

Commit 9ed3f222 ("intel_th: Don't reference unassigned outputs")
fixes a NULL dereference for all masters except the last one ("256+"),
which keeps the stale pointer after the output driver had been unassigned.

Fix the off-by-one.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Fixes: 9ed3f222 ("intel_th: Don't reference unassigned outputs")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/hwtracing/intel_th/gth.c

@@ -597,7 +597,7 @@ static void intel_th_gth_unassign(struct intel_th_device *thdev,
 	othdev->output.port = -1;
 	othdev->output.active = false;
 	gth->output[port].output = NULL;
-	for (master = 0; master < TH_CONFIGURABLE_MASTERS; master++)
+	for (master = 0; master <= TH_CONFIGURABLE_MASTERS; master++)
 		if (gth->master[master] == port)
 			gth->master[master] = -1;
 	spin_unlock(&gth->gth_lock);