stm class: Fix channel free in stm output free path

BugLink: https://bugs.launchpad.net/bugs/1832661

commit ee496da4 upstream.

Number of free masters is not set correctly in stm
free path. Fix this by properly adding the number
of output channels before setting them to 0 in
stm_output_disclaim().

Currently it is equivalent to doing nothing since
master->nr_free is incremented by 0.

Fixes: 7bd1d409 ("stm class: Introduce an abstraction for System Trace Module devices")
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: stable@vger.kernel.org # v4.4
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/hwtracing/stm/core.c

@@ -210,8 +210,8 @@ stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
 	bitmap_release_region(&master->chan_map[0], output->channel,
 			      ilog2(output->nr_chans));
 
-	output->nr_chans = 0;
 	master->nr_free += output->nr_chans;
+	output->nr_chans = 0;
 }
 
 /*