stm class: Fix channel free in stm output free path

commit ee496da4c3915de3232b5f5cd20e21ae3e46fe8d 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: NTingwei Zhang <tingwei@codeaurora.org>
Signed-off-by: NSai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: stable@vger.kernel.org # v4.4
Signed-off-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/stm/core.c

@@ -218,8 +218,8 @@ 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;
 }
 
 /*