ASoC: Intel: Skylake: Fix null ptr dereferenced in skl_tplg_bind_sinks

This patch fixes the below warning form smatch and makes the
skl_tplg_bind_sinks take the next sink as argument which is true
when the current sink is valid

sound/soc/intel/skylake/skl-topology.c:453 skl_tplg_bind_sinks()
	error: we previously assumed 'sink' could be null (see line 452)

sound/soc/intel/skylake/skl-topology.c
   451
   452		if (!sink)
                     ^^^^
New check.  Reversed?

   453			return skl_tplg_bind_sinks(sink, skl, src_mconfig);
                                                   ^^^^ This is
dereferenced inside the function.

   454
   455		return 0;

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>